Song Liu [Wed, 6 Dec 2023 22:40:51 +0000 (14:40 -0800)]
bpf, x86: Adjust arch_prepare_bpf_trampoline return value
x86's implementation of arch_prepare_bpf_trampoline() requires
BPF_INSN_SAFETY buffer space between end of program and image_end. OTOH,
the return value does not include BPF_INSN_SAFETY. This doesn't cause any
real issue at the moment. However, "image" of size retval is not enough for
arch_prepare_bpf_trampoline(). This will cause confusion when we introduce
a new helper arch_bpf_trampoline_size(). To avoid future confusion, adjust
the return value to include BPF_INSN_SAFETY.
Song Liu [Wed, 6 Dec 2023 22:40:50 +0000 (14:40 -0800)]
bpf: Add helpers for trampoline image management
As BPF trampoline of different archs moves from bpf_jit_[alloc|free]_exec()
to bpf_prog_pack_[alloc|free](), we need to use different _alloc, _free for
different archs during the transition. Add the following helpers for this
transition:
void *arch_alloc_bpf_trampoline(unsigned int size);
void arch_free_bpf_trampoline(void *image, unsigned int size);
void arch_protect_bpf_trampoline(void *image, unsigned int size);
void arch_unprotect_bpf_trampoline(void *image, unsigned int size);
The fallback version of these helpers require size <= PAGE_SIZE, but they
are only called with size == PAGE_SIZE. They will be called with size <
PAGE_SIZE when arch_bpf_trampoline_size() helper is introduced later.
Signed-off-by: Song Liu <song@kernel.org> Acked-by: Ilya Leoshkevich <iii@linux.ibm.com> Tested-by: Ilya Leoshkevich <iii@linux.ibm.com> # on s390x Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20231206224054.492250-4-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Song Liu [Wed, 6 Dec 2023 22:40:49 +0000 (14:40 -0800)]
bpf: Adjust argument names of arch_prepare_bpf_trampoline()
We are using "im" for "struct bpf_tramp_image" and "tr" for "struct
bpf_trampoline" in most of the code base. The only exception is the
prototype and fallback version of arch_prepare_bpf_trampoline(). Update
them to match the rest of the code base.
We mix "orig_call" and "func_addr" for the argument in different versions
of arch_prepare_bpf_trampoline(). s/orig_call/func_addr/g so they match.
Signed-off-by: Song Liu <song@kernel.org> Acked-by: Ilya Leoshkevich <iii@linux.ibm.com> Tested-by: Ilya Leoshkevich <iii@linux.ibm.com> # on s390x Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20231206224054.492250-3-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Song Liu [Wed, 6 Dec 2023 22:40:48 +0000 (14:40 -0800)]
bpf: Let bpf_prog_pack_free handle any pointer
Currently, bpf_prog_pack_free only can only free pointer to struct
bpf_binary_header, which is not flexible. Add a size argument to
bpf_prog_pack_free so that it can handle any pointer.
Signed-off-by: Song Liu <song@kernel.org> Acked-by: Ilya Leoshkevich <iii@linux.ibm.com> Tested-by: Ilya Leoshkevich <iii@linux.ibm.com> # on s390x Reviewed-by: Björn Töpel <bjorn@rivosinc.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Link: https://lore.kernel.org/r/20231206224054.492250-2-song@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Andrii Nakryiko [Wed, 6 Dec 2023 19:09:20 +0000 (11:09 -0800)]
bpf: rename MAX_BPF_LINK_TYPE into __MAX_BPF_LINK_TYPE for consistency
To stay consistent with the naming pattern used for similar cases in BPF
UAPI (__MAX_BPF_ATTACH_TYPE, etc), rename MAX_BPF_LINK_TYPE into
__MAX_BPF_LINK_TYPE.
Also similar to MAX_BPF_ATTACH_TYPE and MAX_BPF_REG, add:
#define MAX_BPF_LINK_TYPE __MAX_BPF_LINK_TYPE
Not all __MAX_xxx enums have such #define, so I'm not sure if we should
add it or not, but I figured I'll start with a completely backwards
compatible way, and we can drop that, if necessary.
Also adjust a selftest that used MAX_BPF_LINK_TYPE enum.
====================
BPF token and BPF FS-based delegation
This patch set introduces an ability to delegate a subset of BPF subsystem
functionality from privileged system-wide daemon (e.g., systemd or any other
container manager) through special mount options for userns-bound BPF FS to
a *trusted* unprivileged application. Trust is the key here. This
functionality is not about allowing unconditional unprivileged BPF usage.
Establishing trust, though, is completely up to the discretion of respective
privileged application that would create and mount a BPF FS instance with
delegation enabled, as different production setups can and do achieve it
through a combination of different means (signing, LSM, code reviews, etc),
and it's undesirable and infeasible for kernel to enforce any particular way
of validating trustworthiness of particular process.
The main motivation for this work is a desire to enable containerized BPF
applications to be used together with user namespaces. This is currently
impossible, as CAP_BPF, required for BPF subsystem usage, cannot be namespaced
or sandboxed, as a general rule. E.g., tracing BPF programs, thanks to BPF
helpers like bpf_probe_read_kernel() and bpf_probe_read_user() can safely read
arbitrary memory, and it's impossible to ensure that they only read memory of
processes belonging to any given namespace. This means that it's impossible to
have a mechanically verifiable namespace-aware CAP_BPF capability, and as such
another mechanism to allow safe usage of BPF functionality is necessary.BPF FS
delegation mount options and BPF token derived from such BPF FS instance is
such a mechanism. Kernel makes no assumption about what "trusted" constitutes
in any particular case, and it's up to specific privileged applications and
their surrounding infrastructure to decide that. What kernel provides is a set
of APIs to setup and mount special BPF FS instanecs and derive BPF tokens from
it. BPF FS and BPF token are both bound to its owning userns and in such a way
are constrained inside intended container. Users can then pass BPF token FD to
privileged bpf() syscall commands, like BPF map creation and BPF program
loading, to perform such operations without having init userns privileged.
This version incorporates feedback and suggestions ([3]) received on v3 of
this patch set, and instead of allowing to create BPF tokens directly assuming
capable(CAP_SYS_ADMIN), we instead enhance BPF FS to accept a few new
delegation mount options. If these options are used and BPF FS itself is
properly created, set up, and mounted inside the user namespaced container,
user application is able to derive a BPF token object from BPF FS instance,
and pass that token to bpf() syscall. As explained in patch #3, BPF token
itself doesn't grant access to BPF functionality, but instead allows kernel to
do namespaced capabilities checks (ns_capable() vs capable()) for CAP_BPF,
CAP_PERFMON, CAP_NET_ADMIN, and CAP_SYS_ADMIN, as applicable. So it forms one
half of a puzzle and allows container managers and sys admins to have safe and
flexible configuration options: determining which containers get delegation of
BPF functionality through BPF FS, and then which applications within such
containers are allowed to perform bpf() commands, based on namespaces
capabilities.
Previous attempt at addressing this very same problem ([0]) attempted to
utilize authoritative LSM approach, but was conclusively rejected by upstream
LSM maintainers. BPF token concept is not changing anything about LSM
approach, but can be combined with LSM hooks for very fine-grained security
policy. Some ideas about making BPF token more convenient to use with LSM (in
particular custom BPF LSM programs) was briefly described in recent LSF/MM/BPF
2023 presentation ([1]). E.g., an ability to specify user-provided data
(context), which in combination with BPF LSM would allow implementing a very
dynamic and fine-granular custom security policies on top of BPF token. In the
interest of minimizing API surface area and discussions this was relegated to
follow up patches, as it's not essential to the fundamental concept of
delegatable BPF token.
It should be noted that BPF token is conceptually quite similar to the idea of
/dev/bpf device file, proposed by Song a while ago ([2]). The biggest
difference is the idea of using virtual anon_inode file to hold BPF token and
allowing multiple independent instances of them, each (potentially) with its
own set of restrictions. And also, crucially, BPF token approach is not using
any special stateful task-scoped flags. Instead, bpf() syscall accepts
token_fd parameters explicitly for each relevant BPF command. This addresses
main concerns brought up during the /dev/bpf discussion, and fits better with
overall BPF subsystem design.
This patch set adds a basic minimum of functionality to make BPF token idea
useful and to discuss API and functionality. Currently only low-level libbpf
APIs support creating and passing BPF token around, allowing to test kernel
functionality, but for the most part is not sufficient for real-world
applications, which typically use high-level libbpf APIs based on `struct
bpf_object` type. This was done with the intent to limit the size of patch set
and concentrate on mostly kernel-side changes. All the necessary plumbing for
libbpf will be sent as a separate follow up patch set kernel support makes it
upstream.
Another part that should happen once kernel-side BPF token is established, is
a set of conventions between applications (e.g., systemd), tools (e.g.,
bpftool), and libraries (e.g., libbpf) on exposing delegatable BPF FS
instance(s) at well-defined locations to allow applications take advantage of
this in automatic fashion without explicit code changes on BPF application's
side. But I'd like to postpone this discussion to after BPF token concept
lands.
v11->v12:
- enforce exact userns match in bpf_token_capable() and
bpf_token_allow_cmd() checks, for added strictness (Christian);
v10->v11:
- fix BPF FS root check to disallow using bind-mounted subdirectory of BPF
FS instance (Christian);
- further restrict BPF_TOKEN_CREATE command to be executed from inside
exactly the same user namespace as the one used to create BPF FS instance
(Christian);
v9->v10:
- slight adjustments in LSM parts (Paul);
- setting delegate_xxx options require capable(CAP_SYS_ADMIN) (Christian);
- simplify BPF_TOKEN_CREATE UAPI by accepting BPF FS FD directly (Christian);
v8->v9:
- fix issue in selftests due to sys/mount.h header (Jiri);
- fix warning in doc comments in LSM hooks (kernel test robot);
v7->v8:
- add bpf_token_allow_cmd and bpf_token_capable hooks (Paul);
- inline bpf_token_alloc() into bpf_token_create() to prevent accidental
divergence with security_bpf_token_create() hook (Paul);
v6->v7:
- separate patches to refactor bpf_prog_alloc/bpf_map_alloc LSM hooks, as
discussed with Paul, and now they also accept struct bpf_token;
- added bpf_token_create/bpf_token_free to allow LSMs (SELinux,
specifically) to set up security LSM blob (Paul);
- last patch also wires bpf_security_struct setup by SELinux, similar to how
it's done for BPF map/prog, though I'm not sure if that's enough, so worst
case it's easy to drop this patch if more full fledged SELinux
implementation will be done separately;
- small fixes for issues caught by code reviews (Jiri, Hou);
- fix for test_maps test that doesn't use LIBBPF_OPTS() macro (CI);
v5->v6:
- fix possible use of uninitialized variable in selftests (CI);
- don't use anon_inode, instead create one from BPF FS instance (Christian);
- don't store bpf_token inside struct bpf_map, instead pass it explicitly to
map_check_btf(). We do store bpf_token inside prog->aux, because it's used
during verification and even can be checked during attach time for some
program types;
- LSM hooks are left intact pending the conclusion of discussion with Paul
Moore; I'd prefer to do LSM-related changes as a follow up patch set
anyways;
v4->v5:
- add pre-patch unifying CAP_NET_ADMIN handling inside kernel/bpf/syscall.c
(Paul Moore);
- fix build warnings and errors in selftests and kernel, detected by CI and
kernel test robot;
v3->v4:
- add delegation mount options to BPF FS;
- BPF token is derived from the instance of BPF FS and associates itself
with BPF FS' owning userns;
- BPF token doesn't grant BPF functionality directly, it just turns
capable() checks into ns_capable() checks within BPF FS' owning user;
- BPF token cannot be pinned;
v2->v3:
- make BPF_TOKEN_CREATE pin created BPF token in BPF FS, and disallow
BPF_OBJ_PIN for BPF token;
v1->v2:
- fix build failures on Kconfig with CONFIG_BPF_SYSCALL unset;
- drop BPF_F_TOKEN_UNKNOWN_* flags and simplify UAPI (Stanislav).
====================
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:29 +0000 (10:52 -0800)]
bpf,selinux: allocate bpf_security_struct per BPF token
Utilize newly added bpf_token_create/bpf_token_free LSM hooks to
allocate struct bpf_security_struct for each BPF token object in
SELinux. This just follows similar pattern for BPF prog and map.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:28 +0000 (10:52 -0800)]
selftests/bpf: add BPF token-enabled tests
Add a selftest that attempts to conceptually replicate intended BPF
token use cases inside user namespaced container.
Child process is forked. It is then put into its own userns and mountns.
Child creates BPF FS context object. This ensures child userns is
captured as the owning userns for this instance of BPF FS. Given setting
delegation mount options is privileged operation, we ensure that child
cannot set them.
This context is passed back to privileged parent process through Unix
socket, where parent sets up delegation options, creates, and mounts it
as a detached mount. This mount FD is passed back to the child to be
used for BPF token creation, which allows otherwise privileged BPF
operations to succeed inside userns.
We validate that all of token-enabled privileged commands (BPF_BTF_LOAD,
BPF_MAP_CREATE, and BPF_PROG_LOAD) work as intended. They should only
succeed inside the userns if a) BPF token is provided with proper
allowed sets of commands and types; and b) namespaces CAP_BPF and other
privileges are set. Lacking a) or b) should lead to -EPERM failures.
Based on suggested workflow by Christian Brauner ([0]).
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:26 +0000 (10:52 -0800)]
libbpf: add BPF token support to bpf_btf_load() API
Allow user to specify token_fd for bpf_btf_load() API that wraps
kernel's BPF_BTF_LOAD command. This allows loading BTF from unprivileged
process as long as it has BPF token allowing BPF_BTF_LOAD command, which
can be created and delegated by privileged process.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:23 +0000 (10:52 -0800)]
bpf,lsm: add BPF token LSM hooks
Wire up bpf_token_create and bpf_token_free LSM hooks, which allow to
allocate LSM security blob (we add `void *security` field to struct
bpf_token for that), but also control who can instantiate BPF token.
This follows existing pattern for BPF map and BPF prog.
Also add security_bpf_token_allow_cmd() and security_bpf_token_capable()
LSM hooks that allow LSM implementation to control and negate (if
necessary) BPF token's delegation of a specific bpf_cmd and capability,
respectively.
Similarly to bpf_prog_alloc LSM hook, rename and extend bpf_map_alloc
hook into bpf_map_create, taking not just struct bpf_map, but also
bpf_attr and bpf_token, to give a fuller context to LSMs.
Unlike bpf_prog_alloc, there is no need to move the hook around, as it
currently is firing right before allocating BPF map ID and FD, which
seems to be a sweet spot.
But like bpf_prog_alloc/bpf_prog_free combo, make sure that bpf_map_free
LSM hook is called even if bpf_map_create hook returned error, as if few
LSMs are combined together it could be that one LSM successfully
allocated security blob for its needs, while subsequent LSM rejected BPF
map creation. The former LSM would still need to free up LSM blob, so we
need to ensure security_bpf_map_free() is called regardless of the
outcome.
Based on upstream discussion ([0]), rework existing
bpf_prog_alloc_security LSM hook. Rename it to bpf_prog_load and instead
of passing bpf_prog_aux, pass proper bpf_prog pointer for a full BPF
program struct. Also, we pass bpf_attr union with all the user-provided
arguments for BPF_PROG_LOAD command. This will give LSMs as much
information as we can basically provide.
The hook is also BPF token-aware now, and optional bpf_token struct is
passed as a third argument. bpf_prog_load LSM hook is called after
a bunch of sanity checks were performed, bpf_prog and bpf_prog_aux were
allocated and filled out, but right before performing full-fledged BPF
verification step.
bpf_prog_free LSM hook is now accepting struct bpf_prog argument, for
consistency. SELinux code is adjusted to all new names, types, and
signatures.
Note, given that bpf_prog_load (previously bpf_prog_alloc) hook can be
used by some LSMs to allocate extra security blob, but also by other
LSMs to reject BPF program loading, we need to make sure that
bpf_prog_free LSM hook is called after bpf_prog_load/bpf_prog_alloc one
*even* if the hook itself returned error. If we don't do that, we run
the risk of leaking memory. This seems to be possible today when
combining SELinux and BPF LSM, as one example, depending on their
relative ordering.
Also, for BPF LSM setup, add bpf_prog_load and bpf_prog_free to
sleepable LSM hooks list, as they are both executed in sleepable
context. Also drop bpf_prog_load hook from untrusted, as there is no
issue with refcount or anything else anymore, that originally forced us
to add it to untrusted list in c0c852dd1876 ("bpf: Do not mark certain LSM
hook arguments as trusted"). We now trigger this hook much later and it
should not be an issue anymore.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:20 +0000 (10:52 -0800)]
bpf: consistently use BPF token throughout BPF verifier logic
Remove remaining direct queries to perfmon_capable() and bpf_capable()
in BPF verifier logic and instead use BPF token (if available) to make
decisions about privileges.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:19 +0000 (10:52 -0800)]
bpf: take into account BPF token when fetching helper protos
Instead of performing unconditional system-wide bpf_capable() and
perfmon_capable() calls inside bpf_base_func_proto() function (and other
similar ones) to determine eligibility of a given BPF helper for a given
program, use previously recorded BPF token during BPF_PROG_LOAD command
handling to inform the decision.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:18 +0000 (10:52 -0800)]
bpf: add BPF token support to BPF_PROG_LOAD command
Add basic support of BPF token to BPF_PROG_LOAD. Wire through a set of
allowed BPF program types and attach types, derived from BPF FS at BPF
token creation time. Then make sure we perform bpf_token_capable()
checks everywhere where it's relevant.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:17 +0000 (10:52 -0800)]
bpf: add BPF token support to BPF_BTF_LOAD command
Accept BPF token FD in BPF_BTF_LOAD command to allow BTF data loading
through delegated BPF token. BTF loading is a pretty straightforward
operation, so as long as BPF token is created with allow_cmds granting
BPF_BTF_LOAD command, kernel proceeds to parsing BTF data and creating
BTF object.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:16 +0000 (10:52 -0800)]
bpf: add BPF token support to BPF_MAP_CREATE command
Allow providing token_fd for BPF_MAP_CREATE command to allow controlled
BPF map creation from unprivileged process through delegated BPF token.
Wire through a set of allowed BPF map types to BPF token, derived from
BPF FS at BPF token creation time. This, in combination with allowed_cmds
allows to create a narrowly-focused BPF token (controlled by privileged
agent) with a restrictive set of BPF maps that application can attempt
to create.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:15 +0000 (10:52 -0800)]
bpf: introduce BPF token object
Add new kind of BPF kernel object, BPF token. BPF token is meant to
allow delegating privileged BPF functionality, like loading a BPF
program or creating a BPF map, from privileged process to a *trusted*
unprivileged process, all while having a good amount of control over which
privileged operations could be performed using provided BPF token.
This is achieved through mounting BPF FS instance with extra delegation
mount options, which determine what operations are delegatable, and also
constraining it to the owning user namespace (as mentioned in the
previous patch).
BPF token itself is just a derivative from BPF FS and can be created
through a new bpf() syscall command, BPF_TOKEN_CREATE, which accepts BPF
FS FD, which can be attained through open() API by opening BPF FS mount
point. Currently, BPF token "inherits" delegated command, map types,
prog type, and attach type bit sets from BPF FS as is. In the future,
having an BPF token as a separate object with its own FD, we can allow
to further restrict BPF token's allowable set of things either at the
creation time or after the fact, allowing the process to guard itself
further from unintentionally trying to load undesired kind of BPF
programs. But for now we keep things simple and just copy bit sets as is.
When BPF token is created from BPF FS mount, we take reference to the
BPF super block's owning user namespace, and then use that namespace for
checking all the {CAP_BPF, CAP_PERFMON, CAP_NET_ADMIN, CAP_SYS_ADMIN}
capabilities that are normally only checked against init userns (using
capable()), but now we check them using ns_capable() instead (if BPF
token is provided). See bpf_token_capable() for details.
Such setup means that BPF token in itself is not sufficient to grant BPF
functionality. User namespaced process has to *also* have necessary
combination of capabilities inside that user namespace. So while
previously CAP_BPF was useless when granted within user namespace, now
it gains a meaning and allows container managers and sys admins to have
a flexible control over which processes can and need to use BPF
functionality within the user namespace (i.e., container in practice).
And BPF FS delegation mount options and derived BPF tokens serve as
a per-container "flag" to grant overall ability to use bpf() (plus further
restrict on which parts of bpf() syscalls are treated as namespaced).
Note also, BPF_TOKEN_CREATE command itself requires ns_capable(CAP_BPF)
within the BPF FS owning user namespace, rounding up the ns_capable()
story of BPF token.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:14 +0000 (10:52 -0800)]
bpf: add BPF token delegation mount options to BPF FS
Add few new mount options to BPF FS that allow to specify that a given
BPF FS instance allows creation of BPF token (added in the next patch),
and what sort of operations are allowed under BPF token. As such, we get
4 new mount options, each is a bit mask
- `delegate_cmds` allow to specify which bpf() syscall commands are
allowed with BPF token derived from this BPF FS instance;
- if BPF_MAP_CREATE command is allowed, `delegate_maps` specifies
a set of allowable BPF map types that could be created with BPF token;
- if BPF_PROG_LOAD command is allowed, `delegate_progs` specifies
a set of allowable BPF program types that could be loaded with BPF token;
- if BPF_PROG_LOAD command is allowed, `delegate_attachs` specifies
a set of allowable BPF program attach types that could be loaded with
BPF token; delegate_progs and delegate_attachs are meant to be used
together, as full BPF program type is, in general, determined
through both program type and program attach type.
Currently, these mount options accept the following forms of values:
- a special value "any", that enables all possible values of a given
bit set;
- numeric value (decimal or hexadecimal, determined by kernel
automatically) that specifies a bit mask value directly;
- all the values for a given mount option are combined, if specified
multiple times. E.g., `mount -t bpf nodev /path/to/mount -o
delegate_maps=0x1 -o delegate_maps=0x2` will result in a combined 0x3
mask.
Ideally, more convenient (for humans) symbolic form derived from
corresponding UAPI enums would be accepted (e.g., `-o
delegate_progs=kprobe|tracepoint`) and I intend to implement this, but
it requires a bunch of UAPI header churn, so I postponed it until this
feature lands upstream or at least there is a definite consensus that
this feature is acceptable and is going to make it, just to minimize
amount of wasted effort and not increase amount of non-essential code to
be reviewed.
Attentive reader will notice that BPF FS is now marked as
FS_USERNS_MOUNT, which theoretically makes it mountable inside non-init
user namespace as long as the process has sufficient *namespaced*
capabilities within that user namespace. But in reality we still
restrict BPF FS to be mountable only by processes with CAP_SYS_ADMIN *in
init userns* (extra check in bpf_fill_super()). FS_USERNS_MOUNT is added
to allow creating BPF FS context object (i.e., fsopen("bpf")) from
inside unprivileged process inside non-init userns, to capture that
userns as the owning userns. It will still be required to pass this
context object back to privileged process to instantiate and mount it.
This manipulation is important, because capturing non-init userns as the
owning userns of BPF FS instance (super block) allows to use that userns
to constraint BPF token to that userns later on (see next patch). So
creating BPF FS with delegation inside unprivileged userns will restrict
derived BPF token objects to only "work" inside that intended userns,
making it scoped to a intended "container". Also, setting these
delegation options requires capable(CAP_SYS_ADMIN), so unprivileged
process cannot set this up without involvement of a privileged process.
There is a set of selftests at the end of the patch set that simulates
this sequence of steps and validates that everything works as intended.
But careful review is requested to make sure there are no missed gaps in
the implementation and testing.
This somewhat subtle set of aspects is the result of previous
discussions ([0]) about various user namespace implications and
interactions with BPF token functionality and is necessary to contain
BPF token inside intended user namespace.
Andrii Nakryiko [Thu, 30 Nov 2023 18:52:13 +0000 (10:52 -0800)]
bpf: align CAP_NET_ADMIN checks with bpf_capable() approach
Within BPF syscall handling code CAP_NET_ADMIN checks stand out a bit
compared to CAP_BPF and CAP_PERFMON checks. For the latter, CAP_BPF or
CAP_PERFMON are checked first, but if they are not set, CAP_SYS_ADMIN
takes over and grants whatever part of BPF syscall is required.
Similar kind of checks that involve CAP_NET_ADMIN are not so consistent.
One out of four uses does follow CAP_BPF/CAP_PERFMON model: during
BPF_PROG_LOAD, if the type of BPF program is "network-related" either
CAP_NET_ADMIN or CAP_SYS_ADMIN is required to proceed.
But in three other cases CAP_NET_ADMIN is required even if CAP_SYS_ADMIN
is set:
- when creating DEVMAP/XDKMAP/CPU_MAP maps;
- when attaching CGROUP_SKB programs;
- when handling BPF_PROG_QUERY command.
This patch is changing the latter three cases to follow BPF_PROG_LOAD
model, that is allowing to proceed under either CAP_NET_ADMIN or
CAP_SYS_ADMIN.
This also makes it cleaner in subsequent BPF token patches to switch
wholesomely to a generic bpf_token_capable(int cap) check, that always
falls back to CAP_SYS_ADMIN if requested capability is missing.
====================
Complete BPF verifier precision tracking support for register spills
Add support to BPF verifier to track and support register spill/fill to/from
stack regardless if it was done through read-only R10 register (which is the
only form supported today), or through a general register after copying R10
into it, while also potentially modifying offset.
Once we add register this generic spill/fill support to precision
backtracking, we can take advantage of it to stop doing eager STACK_ZERO
conversion on register spill. Instead we can rely on (im)precision of spilled
const zero register to improve verifier state pruning efficiency. This
situation of using const zero register to initialize stack slots is very
common with __builtin_memset() usage or just zero-initializing variables on
the stack, and it causes unnecessary state duplication, as that STACK_ZERO
knowledge is often not necessary for correctness, as those zero values are
never used in precise context. Thus, relying on register imprecision helps
tremendously, especially in real-world BPF programs.
To make spilled const zero register behave completely equivalently to
STACK_ZERO, we need to improve few other small pieces, which is done in the
second part of the patch set. See individual patches for details. There are
also two small bug fixes spotted during STACK_ZERO debugging.
The patch set consists of logically three changes:
- patch #1 (and corresponding tests in patch #2) is fixing/impoving precision
propagation for stack spills/fills. This can be landed as a stand-alone
improvement;
- patches #3 through #9 is improving verification scalability by utilizing
register (im)precision instead of eager STACK_ZERO. These changes depend
on patch #1.
- patch #10 is a memory efficiency improvement to how instruction/jump
history is tracked and maintained. It depends on patch #1, but is not
strictly speaking required, even though I believe it's a good long-term
solution to have a path-dependent per-instruction information. Kind
of like a path-dependent counterpart to path-agnostic insn_aux array.
v3->v3:
- fixed up Fixes tag (Alexei);
- fixed few more selftests to not use BPF_ST instruction in inline asm
directly, checked with CI, it was happy (CI);
v2->v3:
- BPF_ST instruction workaround (Eduard);
- force dereference in added tests to catch problems (Eduard);
- some commit message massaging (Alexei);
v1->v2:
- clean ups, WARN_ONCE(), insn_flags helpers added (Eduard);
- added more selftests for STACK_ZERO/STACK_MISC cases (Eduard);
- a bit more detailed explanation of effect of avoiding STACK_ZERO in favor
of register spill in patch #8 commit (Alexei);
- global shared instruction history refactoring moved to be the last patch
in the series to make it easier to revert it, if applied (Alexei).
====================
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:47 +0000 (10:42 -0800)]
selftests/bpf: validate precision logic in partial_stack_load_preserves_zeros
Enhance partial_stack_load_preserves_zeros subtest with detailed
precision propagation log checks. We know expect fp-16 to be spilled,
initially imprecise, zero const register, which is later marked as
precise even when partial stack slot load is performed, even if it's not
a register fill (!).
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:46 +0000 (10:42 -0800)]
bpf: track aligned STACK_ZERO cases as imprecise spilled registers
Now that precision backtracing is supporting register spill/fill to/from
stack, there is another oportunity to be exploited here: minimizing
precise STACK_ZERO cases. With a simple code change we can rely on
initially imprecise register spill tracking for cases when register
spilled to stack was a known zero.
This is a very common case for initializing on the stack variables,
including rather large structures. Often times zero has no special
meaning for the subsequent BPF program logic and is often overwritten
with non-zero values soon afterwards. But due to STACK_ZERO vs
STACK_MISC tracking, such initial zero initialization actually causes
duplication of verifier states as STACK_ZERO is clearly different than
STACK_MISC or spilled SCALAR_VALUE register.
The effect of this (now) trivial change is huge, as can be seen below.
These are differences between BPF selftests, Cilium, and Meta-internal
BPF object files relative to previous patch in this series. You can see
improvements ranging from single-digit percentage improvement for
instructions and states, all the way to 50-60% reduction for some of
Meta-internal host agent programs, and even some Cilium programs.
For Meta-internal ones I left only the differences for largest BPF
object files by states/instructions, as there were too many differences
in the overall output. All the differences were improvements, reducting
number of states and thus instructions validated.
Note, Meta-internal BPF object file names are not printed below.
Many copies of balancer_ingress are actually many different
configurations of Katran, so they are different BPF programs, which
explains state reduction going from -16% all the way to 31%, depending
on BPF program logic complexity.
I also tooked a closer look at a few small-ish BPF programs to validate
the behavior. Let's take bpf_iter_netrlink.bpf.o (first row below).
While it's just 8 vs 5 states, verifier log is still pretty long to
include it here. But the reduction in states is due to the following
piece of C code:
You can see that in some situations `ino` is zero-initialized, while in
others it's unknown value filled out by bpf_probe_read_kernel(). Before
this change code after if/else branches have to be validated twice. Once
with (precise) ino == 0, due to eager STACK_ZERO logic, and then again
for when ino is just STACK_MISC. But BPF_SEQ_PRINTF() doesn't care about
precise value of ino, so with the change in this patch verifier is able
to prune states from after one of the branches, reducing number of total
states (and instructions) required for successful validation.
Similar principle applies to bigger real-world applications, just at
a much larger scale.
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:45 +0000 (10:42 -0800)]
selftests/bpf: validate zero preservation for sub-slot loads
Validate that 1-, 2-, and 4-byte loads from stack slots not aligned on
8-byte boundary still preserve zero, when loading from all-STACK_ZERO
sub-slots, or when stack sub-slots are covered by spilled register with
known constant zero value.
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:44 +0000 (10:42 -0800)]
bpf: preserve constant zero when doing partial register restore
Similar to special handling of STACK_ZERO, when reading 1/2/4 bytes from
stack from slot that has register spilled into it and that register has
a constant value zero, preserve that zero and mark spilled register as
precise for that. This makes spilled const zero register and STACK_ZERO
cases equivalent in their behavior.
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:42 +0000 (10:42 -0800)]
bpf: preserve STACK_ZERO slots on partial reg spills
Instead of always forcing STACK_ZERO slots to STACK_MISC, preserve it in
situations where this is possible. E.g., when spilling register as
1/2/4-byte subslots on the stack, all the remaining bytes in the stack
slot do not automatically become unknown. If we knew they contained
zeroes, we can preserve those STACK_ZERO markers.
Add a helper mark_stack_slot_misc(), similar to scrub_spilled_slot(),
but that doesn't overwrite either STACK_INVALID nor STACK_ZERO. Note
that we need to take into account possibility of being in unprivileged
mode, in which case STACK_INVALID is forced to STACK_MISC for correctness,
as treating STACK_INVALID as equivalent STACK_MISC is only enabled in
privileged mode.
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:41 +0000 (10:42 -0800)]
bpf: fix check for attempt to corrupt spilled pointer
When register is spilled onto a stack as a 1/2/4-byte register, we set
slot_type[BPF_REG_SIZE - 1] (plus potentially few more below it,
depending on actual spill size). So to check if some stack slot has
spilled register we need to consult slot_type[7], not slot_type[0].
To avoid the need to remember and double-check this in the future, just
use is_spilled_reg() helper.
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:40 +0000 (10:42 -0800)]
selftests/bpf: add stack access precision test
Add a new selftests that validates precision tracking for stack access
instruction, using both r10-based and non-r10-based accesses. For
non-r10 ones we also make sure to have non-zero var_off to validate that
final stack offset is tracked properly in instruction history
information inside verifier.
Andrii Nakryiko [Tue, 5 Dec 2023 18:42:39 +0000 (10:42 -0800)]
bpf: support non-r10 register spill/fill to/from stack in precision tracking
Use instruction (jump) history to record instructions that performed
register spill/fill to/from stack, regardless if this was done through
read-only r10 register, or any other register after copying r10 into it
*and* potentially adjusting offset.
To make this work reliably, we push extra per-instruction flags into
instruction history, encoding stack slot index (spi) and stack frame
number in extra 10 bit flags we take away from prev_idx in instruction
history. We don't touch idx field for maximum performance, as it's
checked most frequently during backtracking.
This change removes basically the last remaining practical limitation of
precision backtracking logic in BPF verifier. It fixes known
deficiencies, but also opens up new opportunities to reduce number of
verified states, explored in the subsequent patches.
There are only three differences in selftests' BPF object files
according to veristat, all in the positive direction (less states).
Note, I avoided renaming jmp_history to more generic insn_hist to
minimize number of lines changed and potential merge conflicts between
bpf and bpf-next trees.
Notice also cur_hist_entry pointer reset to NULL at the beginning of
instruction verification loop. This pointer avoids the problem of
relying on last jump history entry's insn_idx to determine whether we
already have entry for current instruction or not. It can happen that we
added jump history entry because current instruction is_jmp_point(), but
also we need to add instruction flags for stack access. In this case, we
don't want to entries, so we need to reuse last added entry, if it is
present.
Relying on insn_idx comparison has the same ambiguity problem as the one
that was fixed recently in [0], so we avoid that.
Stanislav Fomichev [Mon, 4 Dec 2023 17:44:23 +0000 (09:44 -0800)]
selftests/bpf: Make sure we trigger metadata kfuncs for dst 8080
xdp_metadata test is flaky sometimes:
verify_xsk_metadata:FAIL:rx_hash_type unexpected rx_hash_type: actual 8 != expected 0
Where 8 means XDP_RSS_TYPE_L4_ANY and is exported from veth driver only when
'skb->l4_hash' condition is met. This makes me think that the program is
triggering again for some other packet.
Let's have a filter, similar to xdp_hw_metadata, where we trigger XDP kfuncs
only for UDP packets destined to port 8080.
Fixes: 11614723af26 ("xsk: Add option to calculate TX checksum in SW") Suggested-by: Simon Horman <horms@kernel.org> Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20231204174231.3457705-1-sdf@google.com
Dave Marchevsky [Mon, 4 Dec 2023 21:17:22 +0000 (13:17 -0800)]
selftests/bpf: Test bpf_kptr_xchg stashing of bpf_rb_root
There was some confusion amongst Meta sched_ext folks regarding whether
stashing bpf_rb_root - the tree itself, rather than a single node - was
supported. This patch adds a small test which demonstrates this
functionality: a local kptr with rb_root is created, a node is created
and added to the tree, then the tree is kptr_xchg'd into a mapval.
Alexei Starovoitov [Tue, 5 Dec 2023 01:50:27 +0000 (17:50 -0800)]
Merge branch 'bpf-fix-the-release-of-inner-map'
Hou Tao says:
====================
bpf: Fix the release of inner map
From: Hou Tao <houtao1@huawei.com>
Hi,
The patchset aims to fix the release of inner map in map array or map
htab. The release of inner map is different with normal map. For normal
map, the map is released after the bpf program which uses the map is
destroyed, because the bpf program tracks the used maps. However bpf
program can not track the used inner map because these inner map may be
updated or deleted dynamically, and for now the ref-counter of inner map
is decreased after the inner map is remove from outer map, so the inner
map may be freed before the bpf program, which is accessing the inner
map, exits and there will be use-after-free problem as demonstrated by
patch #6.
The patchset fixes the problem by deferring the release of inner map.
The freeing of inner map is deferred according to the sleepable
attributes of the bpf programs which own the outer map. Patch #1 fixes
the warning when running the newly-added selftest under interpreter
mode. Patch #2 adds more parameters to .map_fd_put_ptr() to prepare for
the fix. Patch #3 fixes the incorrect value of need_defer when freeing
the fd array. Patch #4 fixes the potential use-after-free problem by
using call_rcu_tasks_trace() and call_rcu() to wait for one tasks trace
RCU GP and one RCU GP unconditionally. Patch #5 optimizes the free of
inner map by removing the unnecessary RCU GP waiting. Patch #6 adds a
selftest to demonstrate the potential use-after-free problem. Patch #7
updates a selftest to update outer map in syscall bpf program.
Please see individual patches for more details. And comments are always
welcome.
Change Log:
v5:
* patch #3: rename fd_array_map_delete_elem_with_deferred_free() to
__fd_array_map_delete_elem() (Alexei)
* patch #5: use atomic64_t instead of atomic_t to prevent potential
overflow (Alexei)
* patch #7: use ptr_to_u64() helper instead of force casting to initialize
pointers in bpf_attr (Alexei)
v4: https://lore.kernel.org/bpf/20231130140120.1736235-1-houtao@huaweicloud.com
* patch #2: don't use "deferred", use "need_defer" uniformly
* patch #3: newly-added, fix the incorrect value of need_defer during
fd array free.
* patch #4: doesn't consider the case in which bpf map is not used by
any bpf program and only use sleepable_refcnt to remove
unnecessary tasks trace RCU GP (Alexei)
* patch #4: remove memory barriers added due to cautiousness (Alexei)
v3: https://lore.kernel.org/bpf/20231124113033.503338-1-houtao@huaweicloud.com
* multiple variable renamings (Martin)
* define BPF_MAP_RCU_GP/BPF_MAP_RCU_TT_GP as bit (Martin)
* use call_rcu() and its variants instead of synchronize_rcu() (Martin)
* remove unnecessary mask in bpf_map_free_deferred() (Martin)
* place atomic_or() and the related smp_mb() together (Martin)
* add patch #6 to demonstrate that updating outer map in syscall
program is dead-lock free (Alexei)
* update comments about the memory barrier in bpf_map_fd_put_ptr()
* update commit message for patch #3 and #4 to describe more details
v2: https://lore.kernel.org/bpf/20231113123324.3914612-1-houtao@huaweicloud.com
* defer the invocation of ops->map_free() instead of bpf_map_put() (Martin)
* update selftest to make it being reproducible under JIT mode (Martin)
* remove unnecessary preparatory patches
Hou Tao [Mon, 4 Dec 2023 14:04:25 +0000 (22:04 +0800)]
selftests/bpf: Test outer map update operations in syscall program
Syscall program is running with rcu_read_lock_trace being held, so if
bpf_map_update_elem() or bpf_map_delete_elem() invokes
synchronize_rcu_tasks_trace() when operating on an outer map, there will
be dead-lock, so add a test to guarantee that it is dead-lock free.
Hou Tao [Mon, 4 Dec 2023 14:04:24 +0000 (22:04 +0800)]
selftests/bpf: Add test cases for inner map
Add test cases to test the race between the destroy of inner map due to
map-in-map update and the access of inner map in bpf program. The
following 4 combinations are added:
(1) array map in map array + bpf program
(2) array map in map array + sleepable bpf program
(3) array map in map htab + bpf program
(4) array map in map htab + sleepable bpf program
Before applying the fixes, when running `./test_prog -a map_in_map`, the
following error was reported:
==================================================================
BUG: KASAN: slab-use-after-free in array_map_update_elem+0x48/0x3e0
Read of size 4 at addr ffff888114f33824 by task test_progs/1858
CPU: 1 PID: 1858 Comm: test_progs Tainted: G O 6.6.0+ #7
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
Call Trace:
<TASK>
dump_stack_lvl+0x4a/0x90
print_report+0xd2/0x620
kasan_report+0xd1/0x110
__asan_load4+0x81/0xa0
array_map_update_elem+0x48/0x3e0
bpf_prog_be94a9f26772f5b7_access_map_in_array+0xe6/0xf6
trace_call_bpf+0x1aa/0x580
kprobe_perf_func+0xdd/0x430
kprobe_dispatcher+0xa0/0xb0
kprobe_ftrace_handler+0x18b/0x2e0
0xffffffffc02280f7
RIP: 0010:__x64_sys_getpgid+0x1/0x30
......
</TASK>
Hou Tao [Mon, 4 Dec 2023 14:04:23 +0000 (22:04 +0800)]
bpf: Optimize the free of inner map
When removing the inner map from the outer map, the inner map will be
freed after one RCU grace period and one RCU tasks trace grace
period, so it is certain that the bpf program, which may access the
inner map, has exited before the inner map is freed.
However there is no need to wait for one RCU tasks trace grace period if
the outer map is only accessed by non-sleepable program. So adding
sleepable_refcnt in bpf_map and increasing sleepable_refcnt when adding
the outer map into env->used_maps for sleepable program. Although the
max number of bpf program is INT_MAX - 1, the number of bpf programs
which are being loaded may be greater than INT_MAX, so using atomic64_t
instead of atomic_t for sleepable_refcnt. When removing the inner map
from the outer map, using sleepable_refcnt to decide whether or not a
RCU tasks trace grace period is needed before freeing the inner map.
Hou Tao [Mon, 4 Dec 2023 14:04:22 +0000 (22:04 +0800)]
bpf: Defer the free of inner map when necessary
When updating or deleting an inner map in map array or map htab, the map
may still be accessed by non-sleepable program or sleepable program.
However bpf_map_fd_put_ptr() decreases the ref-counter of the inner map
directly through bpf_map_put(), if the ref-counter is the last one
(which is true for most cases), the inner map will be freed by
ops->map_free() in a kworker. But for now, most .map_free() callbacks
don't use synchronize_rcu() or its variants to wait for the elapse of a
RCU grace period, so after the invocation of ops->map_free completes,
the bpf program which is accessing the inner map may incur
use-after-free problem.
Fix the free of inner map by invoking bpf_map_free_deferred() after both
one RCU grace period and one tasks trace RCU grace period if the inner
map has been removed from the outer map before. The deferment is
accomplished by using call_rcu() or call_rcu_tasks_trace() when
releasing the last ref-counter of bpf map. The newly-added rcu_head
field in bpf_map shares the same storage space with work field to
reduce the size of bpf_map.
Fixes: bba1dc0b55ac ("bpf: Remove redundant synchronize_rcu.") Fixes: 638e4b825d52 ("bpf: Allows per-cpu maps and map-in-map in sleepable programs") Signed-off-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/r/20231204140425.1480317-5-houtao@huaweicloud.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Hou Tao [Mon, 4 Dec 2023 14:04:21 +0000 (22:04 +0800)]
bpf: Set need_defer as false when clearing fd array during map free
Both map deletion operation, map release and map free operation use
fd_array_map_delete_elem() to remove the element from fd array and
need_defer is always true in fd_array_map_delete_elem(). For the map
deletion operation and map release operation, need_defer=true is
necessary, because the bpf program, which accesses the element in fd
array, may still alive. However for map free operation, it is certain
that the bpf program which owns the fd array has already been exited, so
setting need_defer as false is appropriate for map free operation.
So fix it by adding need_defer parameter to bpf_fd_array_map_clear() and
adding a new helper __fd_array_map_delete_elem() to handle the map
deletion, map release and map free operations correspondingly.
Hou Tao [Mon, 4 Dec 2023 14:04:20 +0000 (22:04 +0800)]
bpf: Add map and need_defer parameters to .map_fd_put_ptr()
map is the pointer of outer map, and need_defer needs some explanation.
need_defer tells the implementation to defer the reference release of
the passed element and ensure that the element is still alive before
the bpf program, which may manipulate it, exits.
The following three cases will invoke map_fd_put_ptr() and different
need_defer values will be passed to these callers:
1) release the reference of the old element in the map during map update
or map deletion. The release must be deferred, otherwise the bpf
program may incur use-after-free problem, so need_defer needs to be
true.
2) release the reference of the to-be-added element in the error path of
map update. The to-be-added element is not visible to any bpf
program, so it is OK to pass false for need_defer parameter.
3) release the references of all elements in the map during map release.
Any bpf program which has access to the map must have been exited and
released, so need_defer=false will be OK.
These two parameters will be used by the following patches to fix the
potential use-after-free problem for map-in-map.
Hou Tao [Mon, 4 Dec 2023 14:04:19 +0000 (22:04 +0800)]
bpf: Check rcu_read_lock_trace_held() before calling bpf map helpers
These three bpf_map_{lookup,update,delete}_elem() helpers are also
available for sleepable bpf program, so add the corresponding lock
assertion for sleepable bpf program, otherwise the following warning
will be reported when a sleepable bpf program manipulates bpf map under
interpreter mode (aka bpf_jit_enable=0):
This patch set fixes BPF verifier logic around validating and enforcing return
values for BPF programs that have specific range of expected return values.
Both sync and async callbacks have similar logic and are fixes as well.
A few tests are added that would fail without the fixes in this patch set.
Also, while at it, we update retval checking logic to use smin/smax range
instead of tnum, avoiding future potential issues if expected range cannot be
represented precisely by tnum (e.g., [0, 2] is not representable by tnum and
is treated as [0, 3]).
There is a little bit of refactoring to unify async callback and program exit
logic to avoid duplication of checks as much as possible.
v4->v5:
- fix timer_bad_ret test on no-alu32 flavor (CI);
v3->v4:
- add back bpf_func_state rearrangement patch;
- simplified patch #4 as suggested (Shung-Hsi);
v2->v3:
- more carefullly switch from umin/umax to smin/smax;
v1->v2:
- drop tnum from retval checks (Eduard);
- use smin/smax instead of umin/umax (Alexei).
====================
Andrii Nakryiko [Sat, 2 Dec 2023 17:57:05 +0000 (09:57 -0800)]
bpf: simplify tnum output if a fully known constant
Emit tnum representation as just a constant if all bits are known.
Use decimal-vs-hex logic to determine exact format of emitted
constant value, just like it's done for register range values.
For that move tnum_strn() to kernel/bpf/log.c to reuse decimal-vs-hex
determination logic and constants.
Andrii Nakryiko [Sat, 2 Dec 2023 17:57:04 +0000 (09:57 -0800)]
selftests/bpf: adjust global_func15 test to validate prog exit precision
Add one more subtest to global_func15 selftest to validate that
verifier properly marks r0 as precise and avoids erroneous state pruning
of the branch that has return value outside of expected [0, 1] value.
Andrii Nakryiko [Sat, 2 Dec 2023 17:57:03 +0000 (09:57 -0800)]
selftests/bpf: validate async callback return value check correctness
Adjust timer/timer_ret_1 test to validate more carefully verifier logic
of enforcing async callback return value. This test will pass only if
return result is marked precise and read.
Andrii Nakryiko [Sat, 2 Dec 2023 17:57:01 +0000 (09:57 -0800)]
bpf: unify async callback and program retval checks
Use common logic to verify program return values and async callback
return values. This allows to avoid duplication of any extra steps
necessary, like precision marking, which will be added in the next
patch.
Andrii Nakryiko [Sat, 2 Dec 2023 17:56:59 +0000 (09:56 -0800)]
selftests/bpf: add selftest validating callback result is enforced
BPF verifier expects callback subprogs to return values from specified
range (typically [0, 1]). This requires that r0 at exit is both precise
(because we rely on specific value range) and is marked as read
(otherwise state comparison will ignore such register as unimportant).
Add a simple test that validates that all these conditions are enforced.
Andrii Nakryiko [Sat, 2 Dec 2023 17:56:58 +0000 (09:56 -0800)]
bpf: enforce exact retval range on subprog/callback exit
Instead of relying on potentially imprecise tnum representation of
expected return value range for callbacks and subprogs, validate that
smin/smax range satisfy exact expected range of return values.
E.g., if callback would need to return [0, 2] range, tnum can't
represent this precisely and instead will allow [0, 3] range. By
checking smin/smax range, we can make sure that subprog/callback indeed
returns only valid [0, 2] range.
Andrii Nakryiko [Sat, 2 Dec 2023 17:56:57 +0000 (09:56 -0800)]
bpf: enforce precision of R0 on callback return
Given verifier checks actual value, r0 has to be precise, so we need to
propagate precision properly. r0 also has to be marked as read,
otherwise subsequent state comparisons will ignore such register as
unimportant and precision won't really help here.
Andrii Nakryiko [Sat, 2 Dec 2023 17:56:55 +0000 (09:56 -0800)]
bpf: rearrange bpf_func_state fields to save a bit of memory
It's a trivial rearrangement saving 8 bytes. We have 4 bytes of padding
at the end which can be filled with another field without increasing
struct bpf_func_state.
copy_func_state() logic remains correct without any further changes.
Changes v7 => v8:
1. Do not use bpf_dynptr_slice* in the kernel. Add __bpf_dynptr_data* and
use them in ther kernel. (Andrii)
Changes v6 => v7:
1. Change "__const_str" annotation to "__str". (Alexei, Andrii)
2. Add KF_TRUSTED_ARGS flag for both new kfuncs. (KP)
3. Only allow bpf_get_file_xattr() to read xattr with "user." prefix.
4. Add Acked-by from Eric Biggers.
Changes v5 => v6:
1. Let fsverity_init_bpf() return void. (Eric Biggers)
2. Sort things in alphabetic orders. (Eric Biggers)
Changes v4 => v5:
1. Revise commit logs. (Alexei)
Changes v3 => v4:
1. Fix error reported by CI.
2. Update comments of bpf_dynptr_slice* that they may return error pointer.
Changes v2 => v3:
1. Rebase and resolve conflicts.
Changes v1 => v2:
1. Let bpf_get_file_xattr() use const string for arg "name". (Alexei)
2. Add recursion prevention with allowlist. (Alexei)
3. Let bpf_get_file_xattr() use __vfs_getxattr() to avoid recursion,
as vfs_getxattr() calls into other LSM hooks.
4. Do not use dynptr->data directly, use helper insteadd. (Andrii)
5. Fixes with bpf_get_fsverity_digest. (Eric Biggers)
6. Add documentation. (Eric Biggers)
7. Fix some compile warnings. (kernel test robot)
This set enables file verification with BPF LSM and fsverity.
In this solution, fsverity is used to provide reliable and efficient hash
of files; and BPF LSM is used to implement signature verification (against
asymmetric keys), and to enforce access control.
This solution can be used to implement access control in complicated cases.
For example: only signed python binary and signed python script and access
special files/devices/ports.
Song Liu [Wed, 29 Nov 2023 23:44:17 +0000 (15:44 -0800)]
selftests/bpf: Add test that uses fsverity and xattr to sign a file
This selftests shows a proof of concept method to use BPF LSM to enforce
file signature. This test is added to verify_pkcs7_sig, so that some
existing logic can be reused.
This file signature method uses fsverity, which provides reliable and
efficient hash (known as digest) of the file. The file digest is signed
with asymmetic key, and the signature is stored in xattr. At the run time,
BPF LSM reads file digest and the signature, and then checks them against
the public key.
Note that this solution does NOT require FS_VERITY_BUILTIN_SIGNATURES.
fsverity is only used to provide file digest. The signature verification
and access control is all implemented in BPF LSM.
Song Liu [Wed, 29 Nov 2023 23:44:16 +0000 (15:44 -0800)]
selftests/bpf: Add tests for filesystem kfuncs
Add selftests for two new filesystem kfuncs:
1. bpf_get_file_xattr
2. bpf_get_fsverity_digest
These tests simply make sure the two kfuncs work. Another selftest will be
added to demonstrate how to use these kfuncs to verify file signature.
CONFIG_FS_VERITY is added to selftests config. However, this is not
sufficient to guarantee bpf_get_fsverity_digest works. This is because
fsverity need to be enabled at file system level (for example, with tune2fs
on ext4). If local file system doesn't have this feature enabled, just skip
the test.
Song Liu [Wed, 29 Nov 2023 23:44:13 +0000 (15:44 -0800)]
bpf, fsverity: Add kfunc bpf_get_fsverity_digest
fsverity provides fast and reliable hash of files, namely fsverity_digest.
The digest can be used by security solutions to verify file contents.
Add new kfunc bpf_get_fsverity_digest() so that we can access fsverity from
BPF LSM programs. This kfunc is added to fs/verity/measure.c because some
data structure used in the function is private to fsverity
(fs/verity/fsverity_private.h).
To avoid recursion, bpf_get_fsverity_digest is only allowed in BPF LSM
programs.
Song Liu [Wed, 29 Nov 2023 23:44:12 +0000 (15:44 -0800)]
bpf: Add kfunc bpf_get_file_xattr
It is common practice for security solutions to store tags/labels in
xattrs. To implement similar functionalities in BPF LSM, add new kfunc
bpf_get_file_xattr().
The first use case of bpf_get_file_xattr() is to implement file
verifications with asymmetric keys. Specificially, security applications
could use fsverity for file hashes and use xattr to store file signatures.
(kfunc for fsverity hash will be added in a separate commit.)
Currently, only xattrs with "user." prefix can be read with kfunc
bpf_get_file_xattr(). As use cases evolve, we may add a dedicated prefix
for bpf_get_file_xattr().
To avoid recursion, bpf_get_file_xattr can be only called from LSM hooks.
Jeroen van Ingen Schenau [Thu, 30 Nov 2023 12:03:53 +0000 (13:03 +0100)]
selftests/bpf: Fix erroneous bitmask operation
xdp_synproxy_kern.c is a BPF program that generates SYN cookies on
allowed TCP ports and sends SYNACKs to clients, accelerating synproxy
iptables module.
Fix the bitmask operation when checking the status of an existing
conntrack entry within tcp_lookup() function. Do not AND with the bit
position number, but with the bitmask value to check whether the entry
found has the IPS_CONFIRMED flag set.
Shinas Rasheed [Wed, 29 Nov 2023 05:31:31 +0000 (21:31 -0800)]
octeon_ep: set backpressure watermark for RX queues
Set backpressure watermark for hardware RX queues. Backpressure
gets triggered when the available buffers of a hardware RX queue
falls below the set watermark. This backpressure will propagate
to packet processing pipeline in the OCTEON card, so that the host
receives fewer packets and prevents packet dropping at host.
Signed-off-by: Shinas Rasheed <srasheed@marvell.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Dan Carpenter [Tue, 28 Nov 2023 13:13:19 +0000 (16:13 +0300)]
octeon_ep: Fix error code in probe()
Set the error code if octep_ctrl_net_get_mtu() fails. Currently the code
returns success.
Fixes: 0a5f8534e398 ("octeon_ep: get max rx packet length from firmware") Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org> Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org> Reviewed-by: Sathesh B Edara <sedara@marvell.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Shinas Rasheed [Wed, 29 Nov 2023 04:53:48 +0000 (20:53 -0800)]
octeon_ep: support OCTEON CN98 devices
Add PCI Endpoint NIC support for Octeon CN98 devices.
CN98 devices are part of Octeon 9 family products with
similar PCI NIC characteristics to CN93, already supported
driver.
Add CN98 card to the device id table, as well
as support differences in the register fields and
certain usage scenarios such as unload.
Andrew Halaney [Mon, 27 Nov 2023 21:41:10 +0000 (15:41 -0600)]
net: phy: mdio_device: Reset device only when necessary
Currently the phy reset sequence is as shown below for a
devicetree described mdio phy on boot:
1. Assert the phy_device's reset as part of registering
2. Deassert the phy_device's reset as part of registering
3. Deassert the phy_device's reset as part of phy_probe
4. Deassert the phy_device's reset as part of phy_hw_init
The extra two deasserts include waiting the deassert delay afterwards,
which is adding unnecessary delay.
This applies to both possible types of resets (reset controller
reference and a reset gpio) that can be used.
Here's some snipped tracing output using the following command line
params "trace_event=gpio:* trace_options=stacktrace" illustrating
the reset handling and where its coming from:
There's a lot of paths where the device is getting its reset
asserted and deasserted. Let's track the state and only actually
do the assert/deassert when it changes.
We've added 30 non-merge commits during the last 7 day(s) which contain
a total of 58 files changed, 1598 insertions(+), 154 deletions(-).
The main changes are:
1) Add initial TX metadata implementation for AF_XDP with support in mlx5
and stmmac drivers. Two types of offloads are supported right now, that
is, TX timestamp and TX checksum offload, from Stanislav Fomichev with
stmmac implementation from Song Yoong Siang.
2) Change BPF verifier logic to validate global subprograms lazily instead
of unconditionally before the main program, so they can be guarded using
BPF CO-RE techniques, from Andrii Nakryiko.
3) Add BPF link_info support for uprobe multi link along with bpftool
integration for the latter, from Jiri Olsa.
4) Use pkg-config in BPF selftests to determine ld flags which is
in particular needed for linking statically, from Akihiko Odaki.
5) Fix a few BPF selftest failures to adapt to the upcoming LLVM18,
from Yonghong Song.
* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (30 commits)
bpf/tests: Remove duplicate JSGT tests
selftests/bpf: Add TX side to xdp_hw_metadata
selftests/bpf: Convert xdp_hw_metadata to XDP_USE_NEED_WAKEUP
selftests/bpf: Add TX side to xdp_metadata
selftests/bpf: Add csum helpers
selftests/xsk: Support tx_metadata_len
xsk: Add option to calculate TX checksum in SW
xsk: Validate xsk_tx_metadata flags
xsk: Document tx_metadata_len layout
net: stmmac: Add Tx HWTS support to XDP ZC
net/mlx5e: Implement AF_XDP TX timestamp and checksum offload
tools: ynl: Print xsk-features from the sample
xsk: Add TX timestamp and TX checksum offload support
xsk: Support tx_metadata_len
selftests/bpf: Use pkg-config for libelf
selftests/bpf: Override PKG_CONFIG for static builds
selftests/bpf: Choose pkg-config for the target
bpftool: Add support to display uprobe_multi links
selftests/bpf: Add link_info test for uprobe_multi link
selftests/bpf: Use bpf_link__destroy in fill_link_info tests
...
====================
Conflicts:
Documentation/netlink/specs/netdev.yaml: 839ff60df3ab ("net: page_pool: add nlspec for basic access to page pools") 48eb03dd2630 ("xsk: Add TX timestamp and TX checksum offload support")
https://lore.kernel.org/all/20231201094705.1ee3cab8@canb.auug.org.au/
While at it also regen, tree is dirty after: 48eb03dd2630 ("xsk: Add TX timestamp and TX checksum offload support")
looks like code wasn't re-rendered after "render-max" was removed.
- dpaa2: recycle the RX buffer only after all processing done
- rswitch: fix missing dev_kfree_skb_any() in error path
Previous releases - always broken:
- ipv4: fix uaf issue when receiving igmp query packet
- wifi: mac80211: fix debugfs deadlock at device removal time
- bpf:
- sockmap: af_unix stream sockets need to hold ref for pair sock
- netdevsim: don't accept device bound programs
- selftests: fix a char signedness issue
- dsa: mv88e6xxx: fix marvell 6350 probe crash
- octeontx2-pf: restore TC ingress police rules when interface is up
- wangxun: fix memory leak on msix entry
- ravb: keep reverse order of operations in ravb_remove()"
* tag 'net-6.7-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (51 commits)
net: ravb: Keep reverse order of operations in ravb_remove()
net: ravb: Stop DMA in case of failures on ravb_open()
net: ravb: Start TX queues after HW initialization succeeded
net: ravb: Make write access to CXR35 first before accessing other EMAC registers
net: ravb: Use pm_runtime_resume_and_get()
net: ravb: Check return value of reset_control_deassert()
net: libwx: fix memory leak on msix entry
ice: Fix VF Reset paths when interface in a failed over aggregate
bpf, sockmap: Add af_unix test with both sockets in map
bpf, sockmap: af_unix stream sockets need to hold ref for pair sock
tools: ynl-gen: always construct struct ynl_req_state
ethtool: don't propagate EOPNOTSUPP from dumps
ravb: Fix races between ravb_tx_timeout_work() and net related ops
r8169: prevent potential deadlock in rtl8169_close
r8169: fix deadlock on RTL8125 in jumbo mtu mode
neighbour: Fix __randomize_layout crash in struct neighbour
octeontx2-pf: Restore TC ingress police rules when interface is up
octeontx2-pf: Fix adding mbox work queue entry when num_vfs > 64
net: stmmac: xgmac: Disable FPE MMC interrupts
octeontx2-af: Fix possible buffer overflow
...
MMC host:
- cqhci: Fix CQE error recovery path
- sdhci-pci-gli: Fix initialization of LPM
- sdhci-sprd: Fix enabling/disabling of the vqmmc regulator"
* tag 'mmc-v6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc:
mmc: sdhci-sprd: Fix vqmmc not shutting down after the card was pulled
mmc: sdhci-pci-gli: Disable LPM during initialization
mmc: cqhci: Fix task clearing in CQE error recovery
mmc: cqhci: Warn of halt or task clear failure
mmc: block: Retry commands in CQE error recovery
mmc: block: Be sure to wait while busy in CQE error recovery
mmc: cqhci: Increase recovery halt timeout
mmc: block: Do not lose cache flush during CQE error recovery
Linus Torvalds [Thu, 30 Nov 2023 22:57:08 +0000 (07:57 +0900)]
Merge tag 'efi-urgent-for-v6.7-1' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi
Pull EFI fix from Ard Biesheuvel:
- Fix for EFI unaccepted memory handling
* tag 'efi-urgent-for-v6.7-1' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi:
efi/unaccepted: Fix off-by-one when checking for overlapping ranges
Eric Dumazet [Thu, 30 Nov 2023 09:22:59 +0000 (09:22 +0000)]
net: page_pool: fix general protection fault in page_pool_unlist
syzbot was able to trigger a crash [1] in page_pool_unlist()
page_pool_list() only inserts a page pool into a netdev page pool list
if a netdev was set in params.
Even if the kzalloc() call in page_pool_create happens to initialize
pool->user.list, I chose to be more explicit in page_pool_list()
adding one INIT_HLIST_NODE().
We could test in page_pool_unlist() if netdev was set,
but since netdev can be changed to lo, it seems more robust to
check if pool->user.list is hashed before calling hlist_del().
Fixes: 083772c9f972 ("net: page_pool: record pools per netdev") Reported-and-tested-by: syzbot+f9f8efb58a4db2ca98d0@syzkaller.appspotmail.com Signed-off-by: Eric Dumazet <edumazet@google.com> Tested-by: Andrew Lunn <andrew@lunn.ch> Link: https://lore.kernel.org/r/20231130092259.3797753-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
====================
net: ethernet: Convert to platform remove callback returning void
in (implicit) v1 of this series
(https://lore.kernel.org/netdev/20231117091655.872426-1-u.kleine-koenig@pengutronix.de)
I tried to address the resource leaks in the three cpsw drivers. However
this is hard to get right without being able to test the changes. So
here comes a series that just converts all drivers below
drivers/net/ethernet to use .remove_new() and adds a comment about the
potential leaks for someone else to fix the problem.
See commit 5c5a7680e67b ("platform: Provide a remove callback that
returns no value") for an extended explanation and the eventual goal.
The TL;DR; is to prevent bugs like the three noticed here.
Note this series results in no change of behaviour apart from improving
the error message for the three cpsw drivers from
remove callback returned a non-zero value. This will be ignored.
to
Failed to resume device (-ESOMETHING)
====================
Uwe Kleine-König [Tue, 28 Nov 2023 17:38:28 +0000 (18:38 +0100)]
net: ethernet: ezchip: Convert to platform remove callback returning void
The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().
Trivially convert this driver from always returning zero in the remove
callback to the void returning variant.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().
Replace the error path returning a non-zero value by an error message
and a comment that there is more to do. With that this patch results in
no change of behaviour in this driver apart from improving the error
message.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Reviewed-by: Roger Quadros <rogerq@kernel.org> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().
Replace the error path returning a non-zero value by an error message
and a comment that there is more to do. With that this patch results in
no change of behaviour in this driver apart from improving the error
message.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Reviewed-by: Roger Quadros <rogerq@kernel.org> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
The .remove() callback for a platform driver returns an int which makes
many driver authors wrongly assume it's possible to do error handling by
returning an error code. However the value returned is ignored (apart
from emitting a warning) and this typically results in resource leaks.
To improve here there is a quest to make the remove callback return
void. In the first step of this quest all drivers are converted to
.remove_new(), which already returns void. Eventually after all drivers
are converted, .remove_new() will be renamed to .remove().
Replace the error path returning a non-zero value by an error message
and a comment that there is more to do. With that this patch results in
no change of behaviour in this driver apart from improving the error
message.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Reviewed-by: Roger Quadros <rogerq@kernel.org> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
====================
devlink: warn about existing entities during reload-reinit
Recently there has been a couple of attempts from drivers to block
devlink reload in certain situations. Turned out, the drivers do not
properly tear down ports and related netdevs during reload.
To address this, add couple of checks to be done during devlink reload
reinit action. Also, extend documentation to be more explicit.
====================
Jiri Pirko [Tue, 28 Nov 2023 11:52:55 +0000 (12:52 +0100)]
devlink: warn about existing entities during reload-reinit
During reload-reinit, all entities except for params, resources, regions
and health reporter should be removed and re-added. Add a warning to
be triggered in case the driver behaves differently.
Yujie Liu [Thu, 30 Nov 2023 03:40:18 +0000 (11:40 +0800)]
bpf/tests: Remove duplicate JSGT tests
It seems unnecessary that JSGT is tested twice (one before JSGE and one
after JSGE) since others are tested only once. Remove the duplicate JSGT
tests.
Fixes: 0bbaa02b4816 ("bpf/tests: Add tests to check source register zero-extension") Signed-off-by: Yujie Liu <yujie.liu@intel.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com> Link: https://lore.kernel.org/bpf/20231130034018.2144963-1-yujie.liu@intel.com
Paolo Abeni [Thu, 30 Nov 2023 09:59:10 +0000 (10:59 +0100)]
Merge branch 'net-ravb-fixes-for-the-ravb-driver'
Claudiu Beznea says:
====================
net: ravb: Fixes for the ravb driver
This series adds some fixes for ravb driver. Patches in this series
were initilly part of series at [1].
Changes in v2:
- in description of patch 1/6 documented the addition of
out_free_netdev goto label
- collected tags
- s/out_runtime_disable/out_rpm_disable in patch 2/6
- fixed typos in description of patch 6/6
Claudiu Beznea [Tue, 28 Nov 2023 08:04:39 +0000 (10:04 +0200)]
net: ravb: Keep reverse order of operations in ravb_remove()
On RZ/G3S SMARC Carrier II board having RGMII connections b/w Ethernet
MACs and PHYs it has been discovered that doing unbind/bind for ravb
driver in a loop leads to wrong speed and duplex for Ethernet links and
broken connectivity (the connectivity cannot be restored even with
bringing interface down/up). Before doing unbind/bind the Ethernet
interfaces were configured though systemd. The sh instructions used to
do unbind/bind were:
$ cd /sys/bus/platform/drivers/ravb/
$ while :; do echo 11c30000.ethernet > unbind ; \
echo 11c30000.ethernet > bind; done
It has been discovered that there is a race b/w IOCTLs initialized by
systemd at the response of success binding and the
"ravb_write(ndev, CCC_OPC_RESET, CCC)" call in ravb_remove() as
follows:
1/ as a result of bind success the user space open/configures the
interfaces tough an IOCTL; the following stack trace has been
identified on RZ/G3S:
2/ this call may execute concurrently with ravb_remove() as the
unbind/bind operation was executed in a loop
3/ if the operation mode is changed to RESET (through
ravb_write(ndev, CCC_OPC_RESET, CCC) call in ravb_remove())
while the above ravb_open() is in progress it may lead to MAC
(or PHY, or MAC-PHY connection, the right point hasn't been identified
at the moment) to be broken, thus the Ethernet connectivity fails to
restore.
The simple fix for this is to move ravb_write(ndev, CCC_OPC_RESET, CCC))
after unregister_netdev() to avoid resetting the controller while the
netdev interface is still registered.
To avoid future issues in ravb_remove(), the patch follows the proper order
of operations in ravb_remove(): reverse order compared with ravb_probe().
This avoids described races as the IOCTLs as well as unregister_netdev()
(called now at the beginning of ravb_remove()) calls rtnl_lock() before
continuing and IOCTLs check (though devinet_ioctl()) if device is still
registered just after taking the lock:
int devinet_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr)
{
// ...
rtnl_lock();
ret = -ENODEV;
dev = __dev_get_by_name(net, ifr->ifr_name);
if (!dev)
goto done;
Claudiu Beznea [Tue, 28 Nov 2023 08:04:38 +0000 (10:04 +0200)]
net: ravb: Stop DMA in case of failures on ravb_open()
In case ravb_phy_start() returns with error the settings applied in
ravb_dmac_init() are not reverted (e.g. config mode). For this call
ravb_stop_dma() on failure path of ravb_open().
projects / users / jedix / linux-maple.git / log