From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sun, 6 Dec 2020 22:22:45 +0000 (+0000)
Subject: io_uring: fix io_cqring_events()'s noflush
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=59850d226e4907a6f37c1d2fe5ba97546a8691a4;p=linux.git

io_uring: fix io_cqring_events()'s noflush

Checking !list_empty(&ctx->cq_overflow_list) around noflush in
io_cqring_events() is racy, because if it fails but a request overflowed
just after that, io_cqring_overflow_flush() still will be called.

Remove the second check, it shouldn't be a problem for performance,
because there is cq_check_overflow bit check just above.

Cc: <stable@vger.kernel.org> # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c0306f77211a0..f53356ced5ab9 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2329,7 +2329,7 @@ static unsigned io_cqring_events(struct io_ring_ctx *ctx, bool noflush)
 		 * we wake up the task, and the next invocation will flush the
 		 * entries. We cannot safely to it from here.
 		 */
-		if (noflush && !list_empty(&ctx->cq_overflow_list))
+		if (noflush)
 			return -1U;
 
 		io_cqring_overflow_flush(ctx, false, NULL, NULL);