linux-kernel - [PATCH 3.16 189/212] drm/vmwgfx: fix integer overflow in vmw_surface_define

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Message-ID: <lsq.1496331796.362383335@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:43:16 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Thomas Hellstrom" <thellstrom@...are.com>,
        "Li Qiang" <liqiang6-s@....cn>, "Li Qiang" <liq3ea@...il.com>
Subject: [PATCH 3.16 189/212] drm/vmwgfx: fix integer overflow in
 vmw_surface_define_ioctl()

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Li Qiang <liq3ea@...il.com>

commit e7e11f99564222d82f0ce84bd521e57d78a6b678 upstream.

In vmw_surface_define_ioctl(), the 'num_sizes' is the sum of the
'req->mip_levels' array. This array can be assigned any value from
the user space. As both the 'num_sizes' and the array is uint32_t,
it is easy to make 'num_sizes' overflow. The later 'mip_levels' is
used as the loop count. This can lead an oob write. Add the check of
'req->mip_levels' to avoid this.

Signed-off-by: Li Qiang <liqiang6-s@....cn>
Reviewed-by: Thomas Hellstrom <thellstrom@...are.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -711,8 +711,11 @@ int vmw_surface_define_ioctl(struct drm_
 			128;
 
 	num_sizes = 0;
-	for (i = 0; i < DRM_VMW_MAX_SURFACE_FACES; ++i)
+	for (i = 0; i < DRM_VMW_MAX_SURFACE_FACES; ++i) {
+		if (req->mip_levels[i] > DRM_VMW_MAX_MIP_LEVELS)
+			return -EINVAL;
 		num_sizes += req->mip_levels[i];
+	}
 
 	if (num_sizes > DRM_VMW_MAX_SURFACE_FACES * DRM_VMW_MAX_MIP_LEVELS ||
 	    num_sizes == 0)