* [PATCH] io_uring: fix possible deadlock in io_register_iowq_max_workers()
@ 2024-06-04 13:05 Hagar Hemdan
2024-06-04 13:38 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Hagar Hemdan @ 2024-06-04 13:05 UTC (permalink / raw)
Cc: Maximilian Heyne, Norbert Manthey, Hagar Hemdan, Jens Axboe,
Pavel Begunkov, io-uring, linux-kernel
The io_register_iowq_max_workers() function calls io_put_sq_data(),
which acquires the sqd->lock without releasing the uring_lock.
Similar to the commit 009ad9f0c6ee ("io_uring: drop ctx->uring_lock
before acquiring sqd->lock"), this can lead to a potential deadlock
situation.
To resolve this issue, the uring_lock is released before calling
io_put_sq_data(), and then it is re-acquired after the function call.
This change ensures that the locks are acquired in the correct
order, preventing the possibility of a deadlock.
Suggested-by: Maximilian Heyne <[email protected]>
Signed-off-by: Hagar Hemdan <[email protected]>
---
only compile tested.
---
io_uring/register.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/io_uring/register.c b/io_uring/register.c
index ef8c908346a4..c0010a66a6f2 100644
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -355,8 +355,10 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
}
if (sqd) {
+ mutex_unlock(&ctx->uring_lock);
mutex_unlock(&sqd->lock);
io_put_sq_data(sqd);
+ mutex_lock(&ctx->uring_lock);
}
if (copy_to_user(arg, new_count, sizeof(new_count)))
@@ -380,8 +382,10 @@ static __cold int io_register_iowq_max_workers(struct io_ring_ctx *ctx,
return 0;
err:
if (sqd) {
+ mutex_unlock(&ctx->uring_lock);
mutex_unlock(&sqd->lock);
io_put_sq_data(sqd);
+ mutex_lock(&ctx->uring_lock);
}
return ret;
}
--
2.40.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] io_uring: fix possible deadlock in io_register_iowq_max_workers()
2024-06-04 13:05 [PATCH] io_uring: fix possible deadlock in io_register_iowq_max_workers() Hagar Hemdan
@ 2024-06-04 13:38 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2024-06-04 13:38 UTC (permalink / raw)
To: Hagar Hemdan
Cc: Maximilian Heyne, Norbert Manthey, Pavel Begunkov, io-uring,
linux-kernel
On Tue, 04 Jun 2024 13:05:27 +0000, Hagar Hemdan wrote:
> The io_register_iowq_max_workers() function calls io_put_sq_data(),
> which acquires the sqd->lock without releasing the uring_lock.
> Similar to the commit 009ad9f0c6ee ("io_uring: drop ctx->uring_lock
> before acquiring sqd->lock"), this can lead to a potential deadlock
> situation.
>
> To resolve this issue, the uring_lock is released before calling
> io_put_sq_data(), and then it is re-acquired after the function call.
>
> [...]
Applied, thanks!
[1/1] io_uring: fix possible deadlock in io_register_iowq_max_workers()
commit: a59035de589f31f195ed1fff97007d332552a72b
Best regards,
--
Jens Axboe
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2024-06-04 13:38 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2024-06-04 13:05 [PATCH] io_uring: fix possible deadlock in io_register_iowq_max_workers() Hagar Hemdan
2024-06-04 13:38 ` Jens Axboe
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox