Mitigate a possible NULL pointer dereference in bpf_get_local_storage() by disallowing tail call to programs that use cgroup storage. Cgroup storage is allocated lazily when attaching a cgroup bpf program. With tail call, it is possible for a callee BPF program to see a NULL storage pointer if the caller prorgam does not use cgroup storage. Reported-by: Yinhao Hu Reported-by: Kaiyan Mei Reported-by: Dongliang Mu Closes: https://lore.kernel.org/bpf/c9ac63d7-73be-49c5-a4ac-eb07f7521adb@hust.edu.cn/ Signed-off-by: Amery Hung --- kernel/bpf/arraymap.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index 1eeb31c5b317..9c3f86ef9d16 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -884,8 +884,9 @@ int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file, void *key, void *value, u64 map_flags) { struct bpf_array *array = container_of(map, struct bpf_array, map); + u32 i, index = *(u32 *)key, ufd; void *new_ptr, *old_ptr; - u32 index = *(u32 *)key, ufd; + struct bpf_prog *prog; if (map_flags != BPF_ANY) return -EINVAL; @@ -898,6 +899,14 @@ int bpf_fd_array_map_update_elem(struct bpf_map *map, struct file *map_file, if (IS_ERR(new_ptr)) return PTR_ERR(new_ptr); + if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY) { + prog = (struct bpf_prog *)new_ptr; + + for_each_cgroup_storage_type(i) + if (prog->aux->cgroup_storage[i]) + return -EINVAL; + } + if (map->ops->map_poke_run) { mutex_lock(&array->aux->poke_mutex); old_ptr = xchg(array->ptrs + index, new_ptr); -- 2.47.3