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

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Date:   Sun, 4 Feb 2018 09:18:03 -0500
From:   Peter Malone <peter.malone@...il.com>
To:     Mathieu Malaterre <malat@...ian.org>
Cc:     Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        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().

Hi folks,

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.

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>



-- 
Regards,
Peter.