gspca_stream_off() calls the sub-driver's stopN() and stop0()
callbacks unconditionally. These issue USB requests using
gspca_dev->dev, which becomes a dangling pointer once the USB device
has been disconnected and freed, causing a use-after-free when the
video device fd is closed after disconnect.

Add a gspca_dev->present check before calling stopN() and stop0(),
matching the existing check already used for gspca_input_create_urb()
in the same function.

Fixes: 1f5965c4dfd7 ("media: gspca: convert to vb2")
Reported-by: syzbot+537b5eb78cebbff5ea70@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=537b5eb78cebbff5ea70
Tested-by: syzbot+537b5eb78cebbff5ea70@syzkaller.appspotmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 drivers/media/usb/gspca/gspca.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/gspca/gspca.c b/drivers/media/usb/gspca/gspca.c
index 594d73e50b9f..5c33cf397f3d 100644
--- a/drivers/media/usb/gspca/gspca.c
+++ b/drivers/media/usb/gspca/gspca.c
@@ -733,14 +733,14 @@ static void gspca_stream_off(struct gspca_dev *gspca_dev)
 {
 	gspca_dev->streaming = false;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->sd_desc->stopN)
+	if (gspca_dev->present && gspca_dev->sd_desc->stopN)
 		gspca_dev->sd_desc->stopN(gspca_dev);
 	destroy_urbs(gspca_dev);
 	gspca_input_destroy_urb(gspca_dev);
 	gspca_set_alt0(gspca_dev);
 	if (gspca_dev->present)
 		gspca_input_create_urb(gspca_dev);
-	if (gspca_dev->sd_desc->stop0)
+	if (gspca_dev->present && gspca_dev->sd_desc->stop0)
 		gspca_dev->sd_desc->stop0(gspca_dev);
 	gspca_dbg(gspca_dev, D_STREAM, "stream off OK\n");
 }
-- 
2.43.0

On 30/08/2026 11:27, Deepanshu Kartikey wrote:
> gspca_stream_off() calls the sub-driver's stopN() and stop0()
> callbacks unconditionally. These issue USB requests using
> gspca_dev->dev, which becomes a dangling pointer once the USB device
> has been disconnected and freed, causing a use-after-free when the
> video device fd is closed after disconnect.
> 
> Add a gspca_dev->present check before calling stopN() and stop0(),
> matching the existing check already used for gspca_input_create_urb()
> in the same function.
> 
> Fixes: 1f5965c4dfd7 ("media: gspca: convert to vb2")
> Reported-by: syzbot+537b5eb78cebbff5ea70@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=537b5eb78cebbff5ea70
> Tested-by: syzbot+537b5eb78cebbff5ea70@syzkaller.appspotmail.com
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>

This is superseded by:

https://patchwork.linuxtv.org/project/linux-media/patch/20260813031235.2468144-1-shuangpeng.kernel@gmail.com/

That's the correct fix since it forces streaming off before freeing anything.

Regards,

	Hans

> ---
>  drivers/media/usb/gspca/gspca.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/gspca/gspca.c b/drivers/media/usb/gspca/gspca.c
> index 594d73e50b9f..5c33cf397f3d 100644
> --- a/drivers/media/usb/gspca/gspca.c
> +++ b/drivers/media/usb/gspca/gspca.c
> @@ -733,14 +733,14 @@ static void gspca_stream_off(struct gspca_dev *gspca_dev)
>  {
>  	gspca_dev->streaming = false;
>  	gspca_dev->usb_err = 0;
> -	if (gspca_dev->sd_desc->stopN)
> +	if (gspca_dev->present && gspca_dev->sd_desc->stopN)
>  		gspca_dev->sd_desc->stopN(gspca_dev);
>  	destroy_urbs(gspca_dev);
>  	gspca_input_destroy_urb(gspca_dev);
>  	gspca_set_alt0(gspca_dev);
>  	if (gspca_dev->present)
>  		gspca_input_create_urb(gspca_dev);
> -	if (gspca_dev->sd_desc->stop0)
> +	if (gspca_dev->present && gspca_dev->sd_desc->stop0)
>  		gspca_dev->sd_desc->stop0(gspca_dev);
>  	gspca_dbg(gspca_dev, D_STREAM, "stream off OK\n");
>  }