FAILED: patch "[PATCH] wifi: brcmfmac: Fix potential use-after-free issue when" 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 c623b63580880cc742255eaed3d79804c1b91143
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051207-posing-gauze-27af@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From c623b63580880cc742255eaed3d79804c1b91143 Mon Sep 17 00:00:00 2001
From: Marek Szyprowski <[email protected]>
Date: Thu, 16 Apr 2026 11:33:39 +0200
Subject: [PATCH] wifi: brcmfmac: Fix potential use-after-free issue when
stopping watchdog task

Watchdog task might end between send_sig() and kthread_stop() calls, what results in the use-after-free issue. Fix this by increasing watchdog task reference count before calling send_sig() and dropping it by switching to kthread_stop_put().

index 30f6fcb68632..8fb595733b9c 100644
@@ -2476,8 +2476,9 @@ static void brcmf_sdio_bus_stop(struct device *dev)
 	brcmf_dbg(TRACE, "Enter\n");
 
 	if (bus->watchdog_tsk) {
+		get_task_struct(bus->watchdog_tsk);
 		send_sig(SIGTERM, bus->watchdog_tsk, 1);
-		kthread_stop(bus->watchdog_tsk);
+		kthread_stop_put(bus->watchdog_tsk);
 		bus->watchdog_tsk = NULL;
 	}
 

@@ -4567,8 +4568,9 @@ void brcmf_sdio_remove(struct brcmf_sdio *bus)
 	if (bus) {
 		/* Stop watchdog task */
 		if (bus->watchdog_tsk) {
+			get_task_struct(bus->watchdog_tsk);
 			send_sig(SIGTERM, bus->watchdog_tsk, 1);
-			kthread_stop(bus->watchdog_tsk);
+			kthread_stop_put(bus->watchdog_tsk);
 			bus->watchdog_tsk = NULL;
 		}
 

From: Marek Szyprowski <[email protected]>

[ Upstream commit c623b63580880cc742255eaed3d79804c1b91143 ]

Watchdog task might end between send_sig() and kthread_stop() calls, what results in the use-after-free issue. Fix this by increasing watchdog task reference count before calling send_sig() and dropping it by switching to kthread_stop_put().

---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c | 4 ++++
 1 file changed, 4 insertions(+)

index 5006aa8317513..76b2953725c2d 100644
@@ -2474,8 +2474,10 @@ static void brcmf_sdio_bus_stop(struct device *dev)
 	brcmf_dbg(TRACE, "Enter\n");
 
 	if (bus->watchdog_tsk) {
+		get_task_struct(bus->watchdog_tsk);
 		send_sig(SIGTERM, bus->watchdog_tsk, 1);
 		kthread_stop(bus->watchdog_tsk);
+		put_task_struct(bus->watchdog_tsk);
 		bus->watchdog_tsk = NULL;
 	}
 

@@ -4549,8 +4551,10 @@ void brcmf_sdio_remove(struct brcmf_sdio *bus)
 	if (bus) {
 		/* Stop watchdog task */
 		if (bus->watchdog_tsk) {
+			get_task_struct(bus->watchdog_tsk);
 			send_sig(SIGTERM, bus->watchdog_tsk, 1);
 			kthread_stop(bus->watchdog_tsk);
+			put_task_struct(bus->watchdog_tsk);
 			bus->watchdog_tsk = NULL;
 		}
 

2.53.0