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* [PATCH] io_uring: fix io_prep_async_link locking
@ 2021-07-26 13:14 Pavel Begunkov
  2021-07-28 19:49 ` Jens Axboe
  0 siblings, 1 reply; 2+ messages in thread
From: Pavel Begunkov @ 2021-07-26 13:14 UTC (permalink / raw)
  To: Jens Axboe, io-uring; +Cc: asml.silence

io_prep_async_link() may be called after arming a linked timeout,
automatically making it unsafe to traverse the linked list. Guard
with completion_lock if there was a linked timeout.

Cc: [email protected] # 5.9+
Signed-off-by: Pavel Begunkov <[email protected]>
---
 fs/io_uring.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7d995d97beeb..6c2cc374a2a5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1279,8 +1279,17 @@ static void io_prep_async_link(struct io_kiocb *req)
 {
 	struct io_kiocb *cur;
 
-	io_for_each_link(cur, req)
-		io_prep_async_work(cur);
+	if (req->flags & REQ_F_LINK_TIMEOUT) {
+		struct io_ring_ctx *ctx = req->ctx;
+
+		spin_lock_irq(&ctx->completion_lock);
+		io_for_each_link(cur, req)
+			io_prep_async_work(cur);
+		spin_unlock_irq(&ctx->completion_lock);
+	} else {
+		io_for_each_link(cur, req)
+			io_prep_async_work(cur);
+	}
 }
 
 static void io_queue_async_work(struct io_kiocb *req)
-- 
2.32.0


^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH] io_uring: fix io_prep_async_link locking
  2021-07-26 13:14 [PATCH] io_uring: fix io_prep_async_link locking Pavel Begunkov
@ 2021-07-28 19:49 ` Jens Axboe
  0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2021-07-28 19:49 UTC (permalink / raw)
  To: Pavel Begunkov, io-uring

On 7/26/21 7:14 AM, Pavel Begunkov wrote:
> io_prep_async_link() may be called after arming a linked timeout,
> automatically making it unsafe to traverse the linked list. Guard
> with completion_lock if there was a linked timeout.

Don't seem to have emailed this out, but I did apply this the other
day. Thanks!

-- 
Jens Axboe


^ permalink raw reply	[flat|nested] 2+ messages in thread

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