[PATCH] firmware_loader: Fix recursive lock in device_cache_fw_images()

[PATCH] firmware_loader: Fix recursive lock in device_cache_fw_images()

[syzbot]

A recursive locking deadlock can occur in the firmware loader's power
management notification handler.

During system suspend or hibernation preparation, fw_pm_notify() calls
device_cache_fw_images(). This function acquires fw_lock to set the
firmware cache state to FW_LOADER_START_CACHE and then iterates over
all devices using dpm_for_each_dev() while still holding the lock.

For each device, dev_cache_fw_image() schedules asynchronous work to
cache the firmware. If memory allocation for the async work entry fails
(e.g., in out-of-memory conditions), async_schedule_node_domain()
falls back to executing the work function synchronously in the current
thread.

The synchronous execution path (__async_dev_cache_fw_image() ->
cache_firmware() -> request_firmware() -> assign_fw()) attempts
to acquire fw_lock again. Since the current thread already holds
fw_lock, this results in a recursive locking deadlock.

Fix this by releasing fw_lock immediately after updating the cache
state and before calling dpm_for_each_dev(). The lock is only needed
to protect the state update. Concurrent firmware requests will correctly
see the FW_LOADER_START_CACHE state and use the piggyback mechanism,
which is independently protected by its own fwc->name_lock.

Fixes: ac39b3ea73aa ("firmware loader: let caching firmware piggyback on loading firmware")
Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview
Reported-by: syzbot+e70e4c6f6eee43357ba7@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=e70e4c6f6eee43357ba7
Link: https://syzkaller.appspot.com/ai_job?id=8cbf9f7d-812d-4db3-89fa-0aaef3ce3a2f
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>

---
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index a11b30dda..c96312ac2 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -1503,9 +1503,10 @@ static void device_cache_fw_images(void)
 
 	mutex_lock(&fw_lock);
 	fwc->state = FW_LOADER_START_CACHE;
-	dpm_for_each_dev(NULL, dev_cache_fw_image);
 	mutex_unlock(&fw_lock);
 
+	dpm_for_each_dev(NULL, dev_cache_fw_image);
+
 	/* wait for completion of caching firmware for all devices */
 	async_synchronize_full_domain(&fw_cache_domain);
 


base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32
-- 
See https://github.com/google/syzkaller/blob/master/docs/syzbot_ai_patches.md for more information.

Re: [PATCH] firmware_loader: Fix recursive lock in device_cache_fw_images()

[Greg Kroah-Hartman]

On Thu, May 21, 2026 at 11:30:44AM +0000, syzbot wrote:
> A recursive locking deadlock can occur in the firmware loader's power
> management notification handler.
> 
> During system suspend or hibernation preparation, fw_pm_notify() calls
> device_cache_fw_images(). This function acquires fw_lock to set the
> firmware cache state to FW_LOADER_START_CACHE and then iterates over
> all devices using dpm_for_each_dev() while still holding the lock.
> 
> For each device, dev_cache_fw_image() schedules asynchronous work to
> cache the firmware. If memory allocation for the async work entry fails
> (e.g., in out-of-memory conditions), async_schedule_node_domain()
> falls back to executing the work function synchronously in the current
> thread.
> 
> The synchronous execution path (__async_dev_cache_fw_image() ->
> cache_firmware() -> request_firmware() -> assign_fw()) attempts
> to acquire fw_lock again. Since the current thread already holds
> fw_lock, this results in a recursive locking deadlock.
> 
> Fix this by releasing fw_lock immediately after updating the cache
> state and before calling dpm_for_each_dev(). The lock is only needed
> to protect the state update. Concurrent firmware requests will correctly
> see the FW_LOADER_START_CACHE state and use the piggyback mechanism,
> which is independently protected by its own fwc->name_lock.
> 
> Fixes: ac39b3ea73aa ("firmware loader: let caching firmware piggyback on loading firmware")
> Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview
> Reported-by: syzbot+e70e4c6f6eee43357ba7@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=e70e4c6f6eee43357ba7
> Link: https://syzkaller.appspot.com/ai_job?id=8cbf9f7d-812d-4db3-89fa-0aaef3ce3a2f
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>

"syzbot" can not be an author :(