maillist inclusion category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9715 Reference: https://git.kernel.org/bpf/bpf-next/c/3f562c537e9e -------------------------------- Syzkaller reported a storage null-ptr-deref issue after replacing prog. This occurs in the following scenario: 1. prog A, an empty prog, is attached to a cgrp. 2. prog B uses BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE and calls the bpf_get_local_storage helper. 3. link_update is called to replace prog A with prog B. The reason is that __cgroup_bpf_replace fails to alloc and assign the required cgrp storage for the incoming replacement prog. Consequently, the new prog inherits an uninit storage, leading to null-ptr-deref panic when kick the new prog. Fix this by rejecting a link update if new_prog's cgroup storage is incompatible with link->prog. Fixes: 0c991ebc8c69 ("bpf: Implement bpf_prog replacement for an active bpf_cgroup_link") Signed-off-by: Pu Lehui <pulehui@huawei.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Reviewed-by: Amery Hung <ameryhung@gmail.com> Acked-by: Leon Hwang <leon.hwang@linux.dev> Link: https://lore.kernel.org/bpf/20260728132336.2857800-1-pulehui@huaweicloud.com [0] Link: https://lore.kernel.org/bpf/f87b53c0-8f00-45a6-82db-8242fa9b143f@huaweicloud... [1] Link: https://lore.kernel.org/bpf/20260807104403.1013064-1-pulehui@huaweicloud.com Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/cgroup.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 41bd6032c6b4..c044c25eadbd 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -591,6 +591,20 @@ static void replace_effective_prog(struct cgroup *cgrp, } } +static bool cgroup_bpf_storages_compatible(struct bpf_prog *old_prog, + struct bpf_prog *new_prog) +{ + enum bpf_cgroup_storage_type stype; + + for_each_cgroup_storage_type(stype) { + if (old_prog->aux->cgroup_storage[stype] != + new_prog->aux->cgroup_storage[stype]) + return false; + } + + return true; +} + /** * __cgroup_bpf_replace() - Replace link's program and propagate the change * to descendants @@ -628,6 +642,9 @@ static int __cgroup_bpf_replace(struct cgroup *cgrp, if (!found) return -ENOENT; + if (!cgroup_bpf_storages_compatible(link->link.prog, new_prog)) + return -EINVAL; + old_prog = xchg(&link->link.prog, new_prog); replace_effective_prog(cgrp, atype, link); bpf_prog_put(old_prog); -- 2.34.1