From: Hou Tao houtao1@huawei.com
[ Upstream commit 66a7a92e4d0d091e79148a4c6ec15d1da65f4280 ]
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: 20b6cc34ea74 ("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 --- kernel/bpf/hashtab.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index ad09da139589..75f77df910dc 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -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;