FAILED: patch "[PATCH] exec: cancel io_uring requests before de_thread()" failed to apply to 7.2-stable tree

The patch below does not apply to the 7.2-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-7.2.y
git checkout FETCH_HEAD
git cherry-pick -x b42c85c20d84ff3e4f0f027d6596c3b3b4a20657
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026102818-halt-spruce-26fc@gregkh' --subject-prefix 'PATCH 7.2.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From b42c85c20d84ff3e4f0f027d6596c3b3b4a20657 Mon Sep 17 00:00:00 2001
From: Christian Brauner <[email protected]>
Date: Mon, 21 Sep 2026 15:45:01 +0200
Subject: [PATCH] exec: cancel io_uring requests before de_thread()

begin_new_exec() cancels the exec'ing thread's io_uring requests after de_thread() made it the only thread in the thread-group. Now io_uring_task_cancel() runs task work after. If it runs a create_worker_cb() item then a io-wq queued on the thread before the exec creates a new io-wq worker thread.

Said thread joins the thread-group which de_thread() just took down. The io-iwq sticks around until it notices that its workqueue is dying. But code after de_thread() relies on being single-threaded.

Move io_uring_task_cancel() before de_thread() but behind the point of no return. Any worker created during task work run from io_uring_task_cancel() is just a sibling thread that de_thread() will take down and reap.

Once io_uring_task_cancel() returned the thread has neither a task context nor a workqueue left so nothing can add a thread behind de_thread()'s back anymore.

index 745f6eb5279e..bf143ee3acb1 100644
@@ -1148,16 +1148,19 @@ int begin_new_exec(struct linux_binprm * bprm)
 	 */
 	bprm->point_of_no_return = true;
 
+	/*
+	 * Cancel any io_uring activity across execve. This runs task work
+	 * that may still create an io-wq worker, so do it while de_thread()
+	 * can still zap it.
+	 */
+	io_uring_task_cancel();
+
 	/* Make this the only thread in the thread group */
 	retval = de_thread(me);
 	if (retval)
 		goto out;
 	/* see the comment in check_unsafe_exec() */
 	current->fs->in_exec = 0;
-	/*
-	 * Cancel any io_uring activity across execve
-	 */
-	io_uring_task_cancel();
 
 	/* Ensure the files table is not shared. */
 	retval = unshare_files();

From: Christian Brauner <[email protected]>

[ Upstream commit b42c85c20d84ff3e4f0f027d6596c3b3b4a20657 ]

begin_new_exec() cancels the exec'ing thread's io_uring requests after de_thread() made it the only thread in the thread-group. Now io_uring_task_cancel() runs task work after. If it runs a create_worker_cb() item then a io-wq queued on the thread before the exec creates a new io-wq worker thread.

Said thread joins the thread-group which de_thread() just took down. The io-iwq sticks around until it notices that its workqueue is dying. But code after de_thread() relies on being single-threaded.

Move io_uring_task_cancel() before de_thread() but behind the point of no return. Any worker created during task work run from io_uring_task_cancel() is just a sibling thread that de_thread() will take down and reap.

Once io_uring_task_cancel() returned the thread has neither a task context nor a workqueue left so nothing can add a thread behind de_thread()'s back anymore.

---
 fs/exec.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

index a598d48b5ffcc..bd3e3aac90efd 100644
@@ -1145,6 +1145,13 @@ int begin_new_exec(struct linux_binprm * bprm)
 	 */
 	bprm->point_of_no_return = true;
 
+	/*
+	 * Cancel any io_uring activity across execve. This runs task work
+	 * that may still create an io-wq worker, so do it while de_thread()
+	 * can still zap it.
+	 */
+	io_uring_task_cancel();
+
 	/* Make this the only thread in the thread group */
 	retval = de_thread(me);
 	if (retval)

@@ -1161,10 +1168,6 @@ int begin_new_exec(struct linux_binprm * bprm)
 
 	/* see the comment in check_unsafe_exec() */
 	current->fs->in_exec = 0;
-	/*
-	 * Cancel any io_uring activity across execve
-	 */
-	io_uring_task_cancel();
 
 	/* Ensure the files table is not shared. */
 	retval = unshare_files();

2.53.0