FAILED: patch "[PATCH] io_uring: check if iowq is killed before queuing" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x dbd2ca9367eb19bc5e269b8c58b0b1514ada9156
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024122314-twice-deuce-e49d@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From dbd2ca9367eb19bc5e269b8c58b0b1514ada9156 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <[email protected]>
Date: Thu, 19 Dec 2024 19:52:58 +0000
Subject: [PATCH] io_uring: check if iowq is killed before queuing

task work can be executed after the task has gone through io_uring termination, whether it's the final task_work run or the fallback path. In this case, task work will find ->io_wq being already killed and null'ed, which is a problem if it then tries to forward the request to io_queue_iowq(). Make io_queue_iowq() fail requests in this case.

Note that it also checks PF_KTHREAD, because the user can first close a DEFER_TASKRUN ring and shortly after kill the task, in which case ->iowq check would race.

index 432b95ca9c85..d3403c8216db 100644
@@ -514,7 +514,11 @@ static void io_queue_iowq(struct io_kiocb *req)
 	struct io_uring_task *tctx = req->tctx;
 
 	BUG_ON(!tctx);
-	BUG_ON(!tctx->io_wq);
+
+	if ((current->flags & PF_KTHREAD) || !tctx->io_wq) {
+		io_req_task_queue_fail(req, -ECANCELED);
+		return;
+	}
 
 	/* init ->work of the whole link before punting */
 	io_prep_async_link(req);