bpf: sockmap: Require attach_bpf_fd when detaching a program

commit bb0de3131f4c60a9bf976681e0fe4d1e55c7a821 upstream.

The sockmap code currently ignores the value of attach_bpf_fd when
detaching a program. This is contrary to the usual behaviour of
checking that attach_bpf_fd represents the currently attached
program.

Ensure that attach_bpf_fd is indeed the currently attached
program. It turns out that all sockmap selftests already do this,
which indicates that this is unlikely to cause breakage.

Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200629095630.7933-5-lmb@cloudflare.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3bf3835d0e866a261f10adcdd97730fd3955429f..7aa0d8b5aaf0c169f0cc68f53669f8a2c7f9b9c6 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -956,11 +956,14 @@ static inline void bpf_map_offload_map_free(struct bpf_map *map)
 #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */
 
 #if defined(CONFIG_BPF_STREAM_PARSER)
-int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog, u32 which);
+int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
+                        struct bpf_prog *old, u32 which);
 int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog);
+int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype);
 #else
 static inline int sock_map_prog_update(struct bpf_map *map,
-                                      struct bpf_prog *prog, u32 which)
+                                      struct bpf_prog *prog,
+                                      struct bpf_prog *old, u32 which)
 {
        return -EOPNOTSUPP;
 }
@@ -970,6 +973,12 @@ static inline int sock_map_get_from_fd(const union bpf_attr *attr,
 {
        return -EINVAL;
 }
+
+static inline int sock_map_prog_detach(const union bpf_attr *attr,
+                                      enum bpf_prog_type ptype)
+{
+       return -EOPNOTSUPP;
+}
 #endif
 
 #if defined(CONFIG_XDP_SOCKETS)

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 4bdb5e4bbd6a1ef2b47880c627ff83c2b563829e..20f3550b0b11b80199ea1bc085b50476c3ae1366 100644 (file)
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -450,6 +450,19 @@ static inline void psock_set_prog(struct bpf_prog **pprog,
                bpf_prog_put(prog);
 }
 
+static inline int psock_replace_prog(struct bpf_prog **pprog,
+                                    struct bpf_prog *prog,
+                                    struct bpf_prog *old)
+{
+       if (cmpxchg(pprog, old, prog) != old)
+               return -ENOENT;
+
+       if (old)
+               bpf_prog_put(old);
+
+       return 0;
+}
+
 static inline void psock_progs_drop(struct sk_psock_progs *progs)
 {
        psock_set_prog(&progs->msg_parser, NULL);

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 8bc904f9badbc30e7df13e16ee1d24850ea2c4d8..bf03d04a9e2f899dd49f9f15014cd9059b2d4ca7 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2029,10 +2029,10 @@ static int bpf_prog_detach(const union bpf_attr *attr)
                ptype = BPF_PROG_TYPE_CGROUP_DEVICE;
                break;
        case BPF_SK_MSG_VERDICT:
-               return sock_map_get_from_fd(attr, NULL);
+               return sock_map_prog_detach(attr, BPF_PROG_TYPE_SK_MSG);
        case BPF_SK_SKB_STREAM_PARSER:
        case BPF_SK_SKB_STREAM_VERDICT:
-               return sock_map_get_from_fd(attr, NULL);
+               return sock_map_prog_detach(attr, BPF_PROG_TYPE_SK_SKB);
        case BPF_LIRC_MODE2:
                return lirc_prog_detach(attr);
        case BPF_FLOW_DISSECTOR:

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 6bbc118bf00e93f5936adeba6934f2b34940398b..df52061f99f760e96dfc5bab9a9f6ad94c1aa4b4 100644 (file)
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -71,7 +71,42 @@ int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog)
        map = __bpf_map_get(f);
        if (IS_ERR(map))
                return PTR_ERR(map);
-       ret = sock_map_prog_update(map, prog, attr->attach_type);
+       ret = sock_map_prog_update(map, prog, NULL, attr->attach_type);
+       fdput(f);
+       return ret;
+}
+
+int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype)
+{
+       u32 ufd = attr->target_fd;
+       struct bpf_prog *prog;
+       struct bpf_map *map;
+       struct fd f;
+       int ret;
+
+       if (attr->attach_flags)
+               return -EINVAL;
+
+       f = fdget(ufd);
+       map = __bpf_map_get(f);
+       if (IS_ERR(map))
+               return PTR_ERR(map);
+
+       prog = bpf_prog_get(attr->attach_bpf_fd);
+       if (IS_ERR(prog)) {
+               ret = PTR_ERR(prog);
+               goto put_map;
+       }
+
+       if (prog->type != ptype) {
+               ret = -EINVAL;
+               goto put_prog;
+       }
+
+       ret = sock_map_prog_update(map, NULL, prog, attr->attach_type);
+put_prog:
+       bpf_prog_put(prog);
+put_map:
        fdput(f);
        return ret;
 }
@@ -1015,27 +1050,32 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
 }
 
 int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog,
-                        u32 which)
+                        struct bpf_prog *old, u32 which)
 {
        struct sk_psock_progs *progs = sock_map_progs(map);
+       struct bpf_prog **pprog;
 
        if (!progs)
                return -EOPNOTSUPP;
 
        switch (which) {
        case BPF_SK_MSG_VERDICT:
-               psock_set_prog(&progs->msg_parser, prog);
+               pprog = &progs->msg_parser;
                break;
        case BPF_SK_SKB_STREAM_PARSER:
-               psock_set_prog(&progs->skb_parser, prog);
+               pprog = &progs->skb_parser;
                break;
        case BPF_SK_SKB_STREAM_VERDICT:
-               psock_set_prog(&progs->skb_verdict, prog);
+               pprog = &progs->skb_verdict;
                break;
        default:
                return -EOPNOTSUPP;
        }
 
+       if (old)
+               return psock_replace_prog(pprog, prog, old);
+
+       psock_set_prog(pprog, prog);
        return 0;
 }