linux-kernel - Re: [PATCH v2] Fixing arbitrary kernel leak in case FBIOGETCMAP_SPARC in sbusfb_ioctl

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Message-id: <2367982.TLCx2xJjlb@amdc3058>
Date:   Wed, 07 Mar 2018 14:03:54 +0100
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Peter Malone <peter.malone@...il.com>
Cc:     Mathieu Malaterre <malat@...ian.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Fixing arbitrary kernel leak in case
 FBIOGETCMAP_SPARC in sbusfb_ioctl_helper().

On Sunday, February 04, 2018 09:18:03 AM Peter Malone wrote:
> Hi folks,

Hi,

> CVE-2018-6412 has been created for this. Is it possible for you to add
> a note indicating the CVE number when merging the patch?
> 
> I received the CVE number after the patch was created and ack'd, which
> is why I didn't include it in the commit message.

I queued the patch (with Mathieu's ACK and CVE number added to the patch
description) for v4.16, thanks.

> On Wed, Jan 31, 2018 at 10:49 AM, Mathieu Malaterre <malat@...ian.org> wrote:
> > Hi Peter,
> >
> > On Wed, Jan 31, 2018 at 3:57 PM, Peter Malone <peter.malone@...il.com> wrote:
> >> Fixing arbitrary kernel leak in case FBIOGETCMAP_SPARC in
> >> sbusfb_ioctl_helper().
> >>
> >> 'index' is defined as an int in sbusfb_ioctl_helper().
> >> We retrieve this from the user:
> >> if (get_user(index, &c->index) ||
> >>     __get_user(count, &c->count) ||
> >>     __get_user(ured, &c->red) ||
> >>     __get_user(ugreen, &c->green) ||
> >>     __get_user(ublue, &c->blue))
> >>        return -EFAULT;
> >>
> >> and then we use 'index' in the following way:
> >> red = cmap->red[index + i] >> 8;
> >> green = cmap->green[index + i] >> 8;
> >> blue = cmap->blue[index + i] >> 8;
> >>
> >> This is a classic information leak vulnerability. 'index' should be
> >> an unsigned int, given its usage above.
> >>
> >> This patch is straight-forward; it changes 'index' to unsigned int
> >> in two switch-cases: FBIOGETCMAP_SPARC && FBIOPUTCMAP_SPARC.
> >>
> >> Signed-off-by: Peter Malone <peter.malone@...il.com>
> >> ---
> >
> > much better :)
> >
> >> v2: fixed formatting
> >>
> >>  drivers/video/fbdev/sbuslib.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/video/fbdev/sbuslib.c b/drivers/video/fbdev/sbuslib.c
> >> index af6fc97f4ba4..a436d44f1b7f 100644
> >> --- a/drivers/video/fbdev/sbuslib.c
> >> +++ b/drivers/video/fbdev/sbuslib.c
> >> @@ -122,7 +122,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
> >>                 unsigned char __user *ured;
> >>                 unsigned char __user *ugreen;
> >>                 unsigned char __user *ublue;
> >> -               int index, count, i;
> >> +               unsigned int index, count, i;
> >>
> >>                 if (get_user(index, &c->index) ||
> >>                     __get_user(count, &c->count) ||
> >> @@ -161,7 +161,7 @@ int sbusfb_ioctl_helper(unsigned long cmd, unsigned long arg,
> >>                 unsigned char __user *ugreen;
> >>                 unsigned char __user *ublue;
> >>                 struct fb_cmap *cmap = &info->cmap;
> >> -               int index, count, i;
> >> +               unsigned int index, count, i;
> >>                 u8 red, green, blue;
> >>
> >>                 if (get_user(index, &c->index) ||
> >> --
> >> 2.14.3
> >>
> >
> > By just looking at the code and commit message:
> >
> > Acked-by: Mathieu Malaterre <malat@...ian.org>

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics