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 [off-list ref] wrote:

quoted

Hi Peter,

On Wed, Jan 31, 2018 at 3:57 PM, Peter Malone [off-list ref] wrote:

quoted

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 <redacted>
---

much better :)

quoted

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 <redacted>

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