Re: CVE Request: Linux kernel: remote buffer overflow in usbip

[Ignat Korchagin <ignat.korchagin () gmail com>]

Hello,

Yes, I contacted cve-assign () mitre org and they provided me with the
following number:
CVE-2016-3955

Regards,
Ignat

2016-04-19 9:35 GMT+01:00 Greg KH <greg () kroah com>:
> On Tue, Apr 19, 2016 at 10:06:43AM +0200, Marcus Meissner wrote:
> > Hi,
> >
> > https://github.com/torvalds/linux/commit/b348d7dddb6c4fbfc810b7a0626e8ec9e29f7cbb
> >
> > commit b348d7dddb6c4fbfc810b7a0626e8ec9e29f7cbb
> > Author: Ignat Korchagin <ignat.korchagin () gmail com>
> > Date:   Thu Mar 17 18:00:29 2016 +0000
> >
> >     USB: usbip: fix potential out-of-bounds write
> >
> >     Fix potential out-of-bounds write to urb->transfer_buffer
> >     usbip handles network communication directly in the kernel. When receiving a
> >     packet from its peer, usbip code parses headers according to protocol. As
> >     part of this parsing urb->actual_length is filled. Since the input for
> >     urb->actual_length comes from the network, it should be treated as untrusted.
> >     Any entity controlling the network may put any value in the input and the
> >     preallocated urb->transfer_buffer may not be large enough to hold the data.
> >     Thus, the malicious entity is able to write arbitrary data to kernel memory.
> >
> >     Signed-off-by: Ignat Korchagin <ignat.korchagin () gmail com>
> >     Signed-off-by: Greg Kroah-Hartman <gregkh () linuxfoundation org>
> >
> > diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
> > index facaaf0..e40da77 100644
> > --- a/drivers/usb/usbip/usbip_common.c
> > +++ b/drivers/usb/usbip/usbip_common.c
> > @@ -741,6 +741,17 @@ int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
> >         if (!(size > 0))
> >                 return 0;
> >
> > +       if (size > urb->transfer_buffer_length) {
> > +               /* should not happen, probably malicious packet */
> > +               if (ud->side == USBIP_STUB) {
> > +                       usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
> > +                       return 0;
> > +               } else {
> > +                       usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
> > +                       return -EPIPE;
> > +               }
> > +       }
> > +
> >         ret = usbip_recv(ud->tcp_socket, urb->transfer_buffer, size);
> >         if (ret != size) {
> >                 dev_err(&urb->dev->dev, "recv xbuf, %d\n", ret);
> >
> > Our USB developer confirms:
> > https://bugzilla.suse.com/show_bug.cgi?id=975945
> > |The vulnerability is true. If an attacker can get a malicious package
> > |into the connection the kernel will accept all of the data in that
> > |package whether it fits into the buffer or not.
> > |You can scribble about 1k into RAM, albeit at an unpredictable location.
>
> I think Ignat already asked for a CVE for this through some other
> channel, and was going to announce it in some manner.
>
> Ignat, did you do that?
>
> thanks,
>
> greg k-h