Re: [syzbot] KASAN: slab-out-of-bounds Write in usb_hcd_poll_rh_status (2)

[Dmitry Vyukov]

On Fri, 31 Dec 2021 at 03:31, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> [Trimmed CC: list]
>
> On Thu, Dec 30, 2021 at 04:49:18PM -0800, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> > KASAN: slab-out-of-bounds Write in usb_hcd_poll_rh_status
> ...
> > Tested on:
> >
> > commit:         eec4df26 Merge tag 's390-5.16-6' of git://git.kernel.o..
> > git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/
>
> I'm glad to see that the git tree is reported properly, but the commit
> label is too short.  The reproducer bug report had exactly the opposite
> problems!  It said:
>
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit:    eec4df26e24e Merge tag 's390-5.16-6' of git://git.kernel.o..
> > git tree:       upstream
>
> Andrey or Dmitry?  Can you guys unify these two outputs to make both
> lines correct always?

Hi Alan,

This got lost on the mailing list. Filed
https://github.com/google/syzkaller/issues/3147 to track this request.

Thanks

> Moving on...  Important lines from the console log:
>
> [   76.919138][ T4081] usb usb9: usbdev_do_ioctl: BULK
> [   76.924966][ T4081] usb usb9: usbfs: process 4081 (syz-executor189) did not claim interface 0 before use
> [   76.935186][ T4081] usb usb9: ep1 int-in, length 1, timeout 9
> [   76.941355][ T4099] usb usb9: opened by process 4099: syz-executor189
> [   76.942606][ T4087] usb usb9: usbdev_do_ioctl: BULK
> [   76.949968][    C1]
> ==================================================================
> [   76.950070][    C1] BUG: KASAN: slab-out-of-bounds in usb_hcd_poll_rh_status+0x376/0x780
> [   76.950102][    C1] Write of size 2 at addr ffff8880121ae230 by task syz-executor189/4087
>
> It's hard to tell what's really happening.  The suspicious part is the
> "length 1" combined with the "Write of size 2" -- but they refer to
> different processes!
>
> Maybe this diagnostic patch will help a little.
>
> Alan Stern
>
> #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ eec4df26e24e
>
> Index: usb-devel/drivers/usb/core/devio.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/devio.c
> +++ usb-devel/drivers/usb/core/devio.c
> @@ -109,7 +109,7 @@ struct async {
>         u8 bulk_status;
>  };
>
> -static bool usbfs_snoop;
> +static bool usbfs_snoop = true;
>  module_param(usbfs_snoop, bool, S_IRUGO | S_IWUSR);
>  MODULE_PARM_DESC(usbfs_snoop, "true to log all usbfs traffic");
>
> Index: usb-devel/drivers/usb/core/hcd.c
> ===================================================================
> --- usb-devel.orig/drivers/usb/core/hcd.c
> +++ usb-devel/drivers/usb/core/hcd.c
> @@ -809,8 +809,10 @@ static int rh_queue_status (struct usb_h
>         unsigned        len = 1 + (urb->dev->maxchild / 8);
>
>         spin_lock_irqsave (&hcd_root_hub_lock, flags);
> +       dev_info(hcd->self.controller, "rh_queue_status: len %d tblen %d\n",
> +                       len, urb->transfer_buffer_length);
>         if (hcd->status_urb || urb->transfer_buffer_length < len) {
> -               dev_dbg (hcd->self.controller, "not queuing rh status urb\n");
> +               dev_info(hcd->self.controller, "not queuing rh status urb\n");
>                 retval = -EINVAL;
>                 goto done;
>         }
>