linux-kernel - [PATCH 3.2 076/101] drm/vmwgfx: NULL pointer dereference in vmw_surface_define

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Message-ID: <lsq.1496331655.361716276@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:40:55 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Murray McAllister" <murray.mcallister@...omniasec.com>,
        "Sinclair Yeh" <syeh@...are.com>
Subject: [PATCH 3.2 076/101] drm/vmwgfx: NULL pointer dereference in
 vmw_surface_define_ioctl()

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

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

From: Murray McAllister <murray.mcallister@...omniasec.com>

commit 36274ab8c596f1240c606bb514da329add2a1bcd upstream.

Before memory allocations vmw_surface_define_ioctl() checks the
upper-bounds of a user-supplied size, but does not check if the
supplied size is 0.

Add check to avoid NULL pointer dereferences.

Signed-off-by: Murray McAllister <murray.mcallister@...omniasec.com>
Reviewed-by: Sinclair Yeh <syeh@...are.com>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_resource.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
@@ -1307,8 +1307,8 @@ int vmw_surface_define_ioctl(struct drm_
 	for (i = 0; i < DRM_VMW_MAX_SURFACE_FACES; ++i)
 		num_sizes += req->mip_levels[i];
 
-	if (num_sizes > DRM_VMW_MAX_SURFACE_FACES *
-	    DRM_VMW_MAX_MIP_LEVELS)
+	if (num_sizes > DRM_VMW_MAX_SURFACE_FACES * DRM_VMW_MAX_MIP_LEVELS ||
+	    num_sizes == 0)
 		return -EINVAL;
 
 	size = vmw_user_surface_size + 128 +