FAILED: patch "[PATCH] scsi: dc395x: sync the waiting_timer before freeing the host" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 0b1a79f2791a06f139dce5450e487307cf0e241f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026110424-unless-washer-9ef1@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 0b1a79f2791a06f139dce5450e487307cf0e241f Mon Sep 17 00:00:00 2001
From: Fan Wu <[email protected]>
Date: Fri, 11 Sep 2026 02:05:44 +0000
Subject: [PATCH] scsi: dc395x: sync the waiting_timer before freeing the host

The waiting_timer callback re-arms itself and takes the host lock. adapter_uninit() currently stops it with timer_delete(), which does not wait for a callback already running on another CPU. The final scsi_host_put() that frees the host (and the host lock the callback dereferences) runs right after adapter_uninit(), so a concurrent or just re-armed callback can fire after the free, leaving a potential use-after-free window.

Replace timer_delete() with timer_shutdown_sync() at the top of adapter_uninit(), before the host-lock section: the timer is dequeued, a running callback is waited for and rearming is blocked before the chip is halted, so it cannot fire at all once the adapter has ceased to function. Waiting outside the lock avoids the self-deadlock that would result from syncing a callback blocked on the lock we still hold.

No shutdown is needed for selto_timer because it has no reachable armer or callback.

This issue was found by an in-house static analysis tool.

index 10e2078f4a0f..5a4f2713dcfa 100644
@@ -3808,13 +3808,11 @@ static void adapter_uninit_chip(struct AdapterCtlBlk *acb)
 static void adapter_uninit(struct AdapterCtlBlk *acb)
 {
 	unsigned long flags;
-	DC395x_LOCK_IO(acb->scsi_host, flags);
 
-	/* remove timers */
-	if (timer_pending(&acb->waiting_timer))
-		timer_delete(&acb->waiting_timer);
-	if (timer_pending(&acb->selto_timer))
-		timer_delete(&acb->selto_timer);
+	/* Drain the self-rearming timer; must not run under host_lock. */
+	timer_shutdown_sync(&acb->waiting_timer);
+
+	DC395x_LOCK_IO(acb->scsi_host, flags);
 
 	adapter_uninit_chip(acb);
 	adapter_remove_and_free_all_devices(acb);

From: Fan Wu <[email protected]>

[ Upstream commit 0b1a79f2791a06f139dce5450e487307cf0e241f ]

The waiting_timer callback re-arms itself and takes the host lock. adapter_uninit() currently stops it with timer_delete(), which does not wait for a callback already running on another CPU. The final scsi_host_put() that frees the host (and the host lock the callback dereferences) runs right after adapter_uninit(), so a concurrent or just re-armed callback can fire after the free, leaving a potential use-after-free window.

Replace timer_delete() with timer_shutdown_sync() at the top of adapter_uninit(), before the host-lock section: the timer is dequeued, a running callback is waited for and rearming is blocked before the chip is halted, so it cannot fire at all once the adapter has ceased to function. Waiting outside the lock avoids the self-deadlock that would result from syncing a callback blocked on the lock we still hold.

No shutdown is needed for selto_timer because it has no reachable armer or callback.

This issue was found by an in-house static analysis tool.

---
 drivers/scsi/dc395x.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

index d8967bf72ef26..5442713433f9b 100644
@@ -4456,13 +4456,11 @@ static void adapter_uninit_chip(struct AdapterCtlBlk *acb)
 static void adapter_uninit(struct AdapterCtlBlk *acb)
 {
 	unsigned long flags;
-	DC395x_LOCK_IO(acb->scsi_host, flags);
 
-	/* remove timers */
-	if (timer_pending(&acb->waiting_timer))
-		del_timer(&acb->waiting_timer);
-	if (timer_pending(&acb->selto_timer))
-		del_timer(&acb->selto_timer);
+	/* Drain the self-rearming timer; must not run under host_lock. */
+	timer_delete_sync(&acb->waiting_timer);
+
+	DC395x_LOCK_IO(acb->scsi_host, flags);
 
 	adapter_uninit_chip(acb);
 	adapter_remove_and_free_all_devices(acb);

2.53.0