Commit 66a7a92e authored by Hou Tao's avatar Hou Tao Committed by Martin KaFai Lau
Browse files

bpf: Propagate error from htab_lock_bucket() to userspace 



In __htab_map_lookup_and_delete_batch() if htab_lock_bucket() returns
-EBUSY, it will go to next bucket. Going to next bucket may not only
skip the elements in current bucket silently, but also incur
out-of-bound memory access or expose kernel memory to userspace if
current bucket_cnt is greater than bucket_size or zero.

Fixing it by stopping batch operation and returning -EBUSY when
htab_lock_bucket() fails, and the application can retry or skip the busy
batch as needed.

Fixes: 20b6cc34 ("bpf: Avoid hashtab deadlock with map_locked")
Reported-by: default avatarHao Sun <sunhao.th@gmail.com>
Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20220831042629.130006-3-houtao@huaweicloud.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parent 2775da21

kernel/bpf/hashtab.c

+5 −2
Original line number Diff line number Diff line
@@ -1704,8 +1704,11 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map, 
	/* do not grab the lock unless need it (bucket_cnt > 0). */

	if (locked) {

		ret = htab_lock_bucket(htab, b, batch, &flags);

		if (ret)

			goto next_batch;

		if (ret) {

			rcu_read_unlock();

			bpf_enable_instrumentation();

			goto after_loop;

		}

	}



	bucket_cnt = 0;