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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org
Subject: [PATCH 3/6] io_uring: fix racy overflow count reporting
Date: Thu, 30 Jul 2020 18:43:47 +0300	[thread overview]
Message-ID: <ba9c998d27e8e75467b09d8a2716cf6618b7cd93.1596123376.git.asml.silence@gmail.com> (raw)
In-Reply-To: <cover.1596123376.git.asml.silence@gmail.com>

All ->cq_overflow modifications should be under completion_lock,
otherwise it can report a wrong number to the userspace. Fix it in
io_uring_cancel_files().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 11f4ab87e08f..6e2322525da6 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7847,10 +7847,9 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
 				clear_bit(0, &ctx->cq_check_overflow);
 				ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW;
 			}
-			spin_unlock_irq(&ctx->completion_lock);
-
 			WRITE_ONCE(ctx->rings->cq_overflow,
 				atomic_inc_return(&ctx->cached_cq_overflow));
+			spin_unlock_irq(&ctx->completion_lock);
 
 			/*
 			 * Put inflight ref and overflow ref. If that's
-- 
2.24.0


  parent reply	other threads:[~2020-07-30 15:46 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 15:43 [PATCH 0/6] 5.9 small cleanups/fixes Pavel Begunkov
2020-07-30 15:43 ` [PATCH 1/6] io_uring: de-unionise io_kiocb Pavel Begunkov
2020-07-30 15:43 ` [PATCH 2/6] io_uring: deduplicate __io_complete_rw() Pavel Begunkov
2020-07-30 15:43 ` Pavel Begunkov [this message]
2020-07-30 17:18   ` [PATCH 3/6] io_uring: fix racy overflow count reporting Jens Axboe
2020-07-30 17:33     ` Pavel Begunkov
2020-07-30 17:41       ` Jens Axboe
2020-07-30 15:43 ` [PATCH 4/6] io_uring: fix stalled deferred requests Pavel Begunkov
2020-07-30 15:43 ` [PATCH 5/6] io_uring: consolidate *_check_overflow accounting Pavel Begunkov
2020-07-30 15:43 ` [PATCH 6/6] io_uring: get rid of atomic FAA for cq_timeouts Pavel Begunkov
2020-07-30 18:08 ` [PATCH 0/6] 5.9 small cleanups/fixes Jens Axboe
2020-07-31 14:28   ` Pavel Begunkov
2020-07-31 15:10     ` Jens Axboe

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