[PATCH v2] media: uvcvideo: Fix NULL deref on events for uninitialized controls

[Wei Jie LAW]

From: Wei Jie Law <98lawweijie@xxxxxxxxx>

A null-ptr-deref exists in v6.12.105 and upstream. KASAN crash log:

  KASAN: null-ptr-deref in range [0x0000000000000080-0x0000000000000087]
  Workqueue: events uvc_ctrl_status_event_work
  RIP: 0010:uvc_ctrl_status_event+0x105/0x280
   uvc_ctrl_status_event_work+0x82/0x240
   process_one_work+0x66f/0x10b0

XU controls are initialized lazily, on the first UVCIOC_CTRL_MAP or
UVCIOC_CTRL_QUERY.  Until then ctrl->info is all zeroes, so
info.mappings is not a valid list head, list_empty() returns false, and
uvc_ctrl_status_event() walks it from a NULL next pointer.

Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wei Jie Law <98lawweijie@xxxxxxxxx>
Assisted-by: Claude:claude-opus-5
Reviewed-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>

---
Changes in v2:
- dropped comments in code based on review received
- add Reviewed-by from Ricardo Ribalda
- drop the former [2/2] patch as it is a duplicate (out-of-bounds read in
  uvc_ctrl_status_event()): already handled by
  https://lore.kernel.org/linux-media/20260813-uvc-status-11-v1-1-2cf43e9590b0@xxxxxxxxxxxx/

v1: https://lore.kernel.org/all/20260907062819.2519878-2-98lawweijie@xxxxxxxxx/
---
 drivers/media/usb/uvc/uvc_ctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index 3ca108b83f1d..ea28c4e819bd 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -2209,7 +2209,7 @@ bool uvc_ctrl_status_event_async(struct urb *urb, struct uvc_video_chain *chain,
 	struct uvc_device *dev = chain->dev;
 	struct uvc_ctrl_work *w = &dev->async_ctrl;
 
-	if (list_empty(&ctrl->info.mappings))
+	if (!ctrl->initialized || list_empty(&ctrl->info.mappings))
 		return false;
 
 	w->data = data;
-- 
2.43.0