On 21/07/2021 21:43, Pavel Skripkin wrote:
> If em28xx dev has ->dev_next pointer, we need to delete dev_next list node
> from em28xx_extension_devlist on disconnect to avoid UAF bugs and
> corrupted list bugs, since driver frees this pointer on disconnect.
>
> Fixes: 1a23f81b7dc3 ("V4L/DVB (9979): em28xx: move usb probe code to a proper place")
> Reported-and-tested-by: syzbot+a6969ef522a36d3344c9@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
> ---
>
> Changes in v2:
> Previous patch was completely broken. I've done some debugging
> again and found true root case of the reported bug.
>
> ---
> drivers/media/usb/em28xx/em28xx-cards.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index c1e0dccb7408..d56b040e1bd7 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4139,8 +4139,10 @@ static void em28xx_usb_disconnect(struct usb_interface *intf)
>
> em28xx_close_extension(dev);
>
> - if (dev->dev_next)
> + if (dev->dev_next) {
> em28xx_release_resources(dev->dev_next);
> + em28xx_close_extension(dev->dev_next);
Wouldn't it be better to swap these two?
That order is also used for em28xx_close_extension(dev) and em28xx_release_resources(dev).
You do need to store dev->dev_next in a temp variable, though.
Regards,
Hans
> + }
> em28xx_release_resources(dev);
>
> if (dev->dev_next) {
>
