On Thu, 29 Jul 2021 11:45:19 +0200
Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> 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.
>
Hi, Hans!
I don't understand why I need to store dev->dev_next in a temp
variable. I don't see code in em28xx_release_resources() or
em28xx_close_extension() that zeroes this pointer.
With regards,
Pavel Skripkin
