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| author | Leon Hwang <leon.hwang@linux.dev> | 2026-06-05 18:52:47 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2026-06-06 01:21:24 +0300 |
| commit | e2a49fdb1beed150125b4104c90eb2a96ec7f63a (patch) | |
| tree | 81cd63b4a46259e013b857436bb5847c77b39399 /include | |
| parent | bbb5e2e31a5476d376ce1d0004c6168585fe1a7f (diff) | |
| download | linux-e2a49fdb1beed150125b4104c90eb2a96ec7f63a.tar.xz | |
bpf: Check tail zero of bpf_map_info
Since there're 4 bytes padding at the end of struct bpf_map_info, they
won't be checked by bpf_check_uarg_tail_zero().
pahole -C bpf_map_info ./vmlinux
struct bpf_map_info {
...
__u64 hash __attribute__((__aligned__(8))); /* 88 8 */
__u32 hash_size; /* 96 4 */
/* size: 104, cachelines: 2, members: 18 */
/* padding: 4 */
/* forced alignments: 1 */
/* last cacheline: 40 bytes */
} __attribute__((__aligned__(8)));
If a future kernel extension adds a new 4-byte field, older userspace
programs allocating this structure on the stack might inadvertently pass
uninitialized stack garbage into the new field, permanently breaking
backward compatibility. -- sashiko [1]
Fix it by changing sizeof(info) to
offsetofend(struct bpf_map_info, hash_size).
And, add "__u32 :32" to the tail of struct bpf_map_info.
[1] https://lore.kernel.org/bpf/20260513224823.6494FC19425@smtp.kernel.org/
Fixes: ea2e6467ac36 ("bpf: Return hashes of maps in BPF_OBJ_GET_INFO_BY_FD")
Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Link: https://lore.kernel.org/r/20260605155249.20772-2-leon.hwang@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/bpf.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index bed9b1b4d5ef..e1730f449d9e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -6733,6 +6733,7 @@ struct bpf_map_info { __u64 map_extra; __aligned_u64 hash; __u32 hash_size; + __u32 :32; } __attribute__((aligned(8))); struct bpf_btf_info { |