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From: Pavel Begunkov <[email protected]>
To: Marco Elver <[email protected]>, [email protected]
Cc: syzbot <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected]
Subject: Re: [syzbot] KCSAN: data-race in __io_uring_cancel / io_uring_try_cancel_requests
Date: Wed, 26 May 2021 17:29:44 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 5/26/21 4:52 PM, Marco Elver wrote:
> Due to some moving around of code, the patch lost the actual fix (using
> atomically read io_wq) -- so here it is again ... hopefully as intended.
> :-)

"fortify" damn it... It was synchronised with &ctx->uring_lock
before, see io_uring_try_cancel_iowq() and io_uring_del_tctx_node(),
so should not clear before *del_tctx_node()

The fix should just move it after this sync point. Will you send
it out as a patch?

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7db6aaf31080..b76ba26b4c6c 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9075,11 +9075,12 @@ static void io_uring_clean_tctx(struct io_uring_task *tctx)
 	struct io_tctx_node *node;
 	unsigned long index;
 
-	tctx->io_wq = NULL;
 	xa_for_each(&tctx->xa, index, node)
 		io_uring_del_tctx_node(index);
-	if (wq)
+	if (wq) {
+		tctx->io_wq = NULL;
 		io_wq_put_and_exit(wq);
+	}
 }
 
 static s64 tctx_inflight(struct io_uring_task *tctx, bool tracked)

 
-- 
Pavel Begunkov

  reply	other threads:[~2021-05-26 16:29 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-26 15:44 [syzbot] KCSAN: data-race in __io_uring_cancel / io_uring_try_cancel_requests syzbot
2021-05-26 15:48 ` Marco Elver
2021-05-26 15:52   ` Marco Elver
2021-05-26 16:29     ` Pavel Begunkov [this message]
2021-05-26 16:33       ` Pavel Begunkov
2021-05-26 16:36       ` Marco Elver
2021-05-26 20:31         ` Pavel Begunkov
2021-05-27  9:32           ` Marco Elver
2021-05-27 10:05             ` Pavel Begunkov

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