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bpf: Tighten cgroup storage cookie checks for prog arrays

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The fix in commit abad3d0bad ("bpf: Fix oob access in cgroup local
storage") is still incomplete. The prog-array compatibility check
treats a program with no cgroup storage as compatible with any stored
storage cookie. This allows a storage-less program to bridge a tail
call chain between an entry program and a storage-using callee even
though cgroup local storage at runtime still follows the caller's
context, that is, A -> B(no storage) -> C(storage) path.

Requiring exact cookie equality would break the legitimate case of a
storage-less leaf program being tail called from a storage-using one.
Instead, only accept a zero storage cookie if the program cannot
perform tail calls itself. This keeps A -> B(no storage) working
while rejecting the A -> B(no storage) -> C(storage) bridge.

Fixes: abad3d0bad ("bpf: Fix oob access in cgroup local storage")
Reported-by: Lin Ma <malin89@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260610105539.705887-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann 2026-06-10 12:55:38 +02:00 committed by Alexei Starovoitov
parent 2e8ad1ff71
commit 10627ddc01
1 changed files with 1 additions and 1 deletions
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2
kernel/bpf/core.c
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@ -2481,7 +2481,7 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map,
cookie = aux->cgroup_storage[i] ?
aux->cgroup_storage[i]->cookie : 0;
ret = map->owner->storage_cookie[i] == cookie ||
!cookie;
(!cookie && !aux->tail_call_reachable);
}
if (ret &&
map->owner->attach_func_proto != aux->attach_func_proto) {