From: Daniel Borkmann Date: Wed, 10 Jun 2026 10:55:38 +0000 (+0200) Subject: bpf: Tighten cgroup storage cookie checks for prog arrays X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=10627ddc0167aab5c1c390a10ef461e9937aba08;p=thirdparty%2Flinux.git bpf: Tighten cgroup storage cookie checks for prog arrays The fix in commit abad3d0bad72 ("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: abad3d0bad72 ("bpf: Fix oob access in cgroup local storage") Reported-by: Lin Ma Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20260610105539.705887-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index a656a8572bdb..649cce41e13f 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -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) {