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bpf: Propagate error from htab_lock_bucket() to userspace

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[ Upstream commit 66a7a92e4d ]

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: 20b6cc34ea ("bpf: Avoid hashtab deadlock with map_locked")
Reported-by: Hao Sun <sunhao.th@gmail.com>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20220831042629.130006-3-houtao@huaweicloud.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Hou Tao 2022-08-31 12:26:28 +08:00 committed by Greg Kroah-Hartman
parent 9f483179e6
commit 4f1f39a8f1
1 changed files with 5 additions and 2 deletions
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7
kernel/bpf/hashtab.c
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@ -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;