6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Borkmann daniel@iogearbox.net
[ Upstream commit abad3d0bad72a52137e0c350c59542d75ae4f513 ]
Lonial reported that an out-of-bounds access in cgroup local storage can be crafted via tail calls. Given two programs each utilizing a cgroup local storage with a different value size, and one program doing a tail call into the other. The verifier will validate each of the indivial programs just fine. However, in the runtime context the bpf_cg_run_ctx holds an bpf_prog_array_item which contains the BPF program as well as any cgroup local storage flavor the program uses. Helpers such as bpf_get_local_storage() pick this up from the runtime context:
ctx = container_of(current->bpf_ctx, struct bpf_cg_run_ctx, run_ctx); storage = ctx->prog_item->cgroup_storage[stype];
if (stype == BPF_CGROUP_STORAGE_SHARED) ptr = &READ_ONCE(storage->buf)->data[0]; else ptr = this_cpu_ptr(storage->percpu_buf);
For the second program which was called from the originally attached one, this means bpf_get_local_storage() will pick up the former program's map, not its own. With mismatching sizes, this can result in an unintended out-of-bounds access.
To fix this issue, we need to extend bpf_map_owner with an array of storage_cookie[] to match on i) the exact maps from the original program if the second program was using bpf_get_local_storage(), or ii) allow the tail call combination if the second program was not using any of the cgroup local storage maps.
Fixes: 7d9c3427894f ("bpf: Make cgroup storages shared between programs on the same cgroup") Reported-by: Lonial Con kongln9170@gmail.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/r/20250730234733.530041-4-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/bpf.h | 1 + kernel/bpf/core.c | 15 +++++++++++++++ 2 files changed, 16 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index b8e0204992857..83da9c81fa86a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -267,6 +267,7 @@ struct bpf_map_owner { enum bpf_prog_type type; bool jited; bool xdp_has_frags; + u64 storage_cookie[MAX_BPF_CGROUP_STORAGE_TYPE]; const struct btf_type *attach_func_proto; };
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index c3369c66eae8f..3618be05fc352 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2263,7 +2263,9 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map, { enum bpf_prog_type prog_type = resolve_prog_type(fp); struct bpf_prog_aux *aux = fp->aux; + enum bpf_cgroup_storage_type i; bool ret = false; + u64 cookie;
if (fp->kprobe_override) return ret; @@ -2278,11 +2280,24 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map, map->owner->jited = fp->jited; map->owner->xdp_has_frags = aux->xdp_has_frags; map->owner->attach_func_proto = aux->attach_func_proto; + for_each_cgroup_storage_type(i) { + map->owner->storage_cookie[i] = + aux->cgroup_storage[i] ? + aux->cgroup_storage[i]->cookie : 0; + } ret = true; } else { ret = map->owner->type == prog_type && map->owner->jited == fp->jited && map->owner->xdp_has_frags == aux->xdp_has_frags; + for_each_cgroup_storage_type(i) { + if (!ret) + break; + cookie = aux->cgroup_storage[i] ? + aux->cgroup_storage[i]->cookie : 0; + ret = map->owner->storage_cookie[i] == cookie || + !cookie; + } if (ret && map->owner->attach_func_proto != aux->attach_func_proto) { switch (prog_type) {