bpf: Resolve fext program type when checking map compatibility

[ Upstream commit 1c123c567fb138ebd187480b7fc0610fcb0851f5 ]

The bpf_prog_map_compatible() check makes sure that BPF program types are
not mixed inside BPF map types that can contain programs (tail call maps,
cpumaps and devmaps). It does this by setting the fields of the map->owner
struct to the values of the first program being checked against, and
rejecting any subsequent programs if the values don't match.

One of the values being set in the map owner struct is the program type,
and since the code did not resolve the prog type for fext programs, the map
owner type would be set to PROG_TYPE_EXT and subsequent loading of programs
of the target type into the map would fail.

This bug is seen in particular for XDP programs that are loaded as
PROG_TYPE_EXT using libxdp; these cannot insert programs into devmaps and
cpumaps because the check fails as described above.

Fix the bug by resolving the fext program type to its target program type
as elsewhere in the verifier.

v3:
- Add Yonghong's ACK

Fixes: f45d5b6ce2e8 ("bpf: generalise tail call map compatibility check")
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20221214230254.790066-1-toke@redhat.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 9e1e6965f40747e5097e6e817d4f878582266a25..0eb8f035b3d9f2c3c999bc5124776ac9988c88b9 100644 (file)
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -642,7 +642,7 @@ static inline u32 type_flag(u32 type)
 }
 
 /* only use after check_attach_btf_id() */
-static inline enum bpf_prog_type resolve_prog_type(struct bpf_prog *prog)
+static inline enum bpf_prog_type resolve_prog_type(const struct bpf_prog *prog)
 {
        return prog->type == BPF_PROG_TYPE_EXT ?
                prog->aux->dst_prog->type : prog->type;

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 25a54e04560e5370635bd31dd007db754ecfae46..17ab3e15ac25f12fb06c60142c9efc9a82a3e2c6 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2088,6 +2088,7 @@ static unsigned int __bpf_prog_ret0_warn(const void *ctx,
 bool bpf_prog_map_compatible(struct bpf_map *map,
                             const struct bpf_prog *fp)
 {
+       enum bpf_prog_type prog_type = resolve_prog_type(fp);
        bool ret;
 
        if (fp->kprobe_override)
@@ -2098,12 +2099,12 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
                /* There's no owner yet where we could check for
                 * compatibility.
                 */
-               map->owner.type  = fp->type;
+               map->owner.type  = prog_type;
                map->owner.jited = fp->jited;
                map->owner.xdp_has_frags = fp->aux->xdp_has_frags;
                ret = true;
        } else {
-               ret = map->owner.type  == fp->type &&
+               ret = map->owner.type  == prog_type &&
                      map->owner.jited == fp->jited &&
                      map->owner.xdp_has_frags == fp->aux->xdp_has_frags;
        }