linux-kernel - [PATCH] drm/vmwgfx: Check check that number of mip levels is above zero in vmw_surface_define

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Message-Id: <20170324153710.8706-1-vdronov@redhat.com>
Date:   Fri, 24 Mar 2017 16:37:10 +0100
From:   Vladis Dronov <vdronov@...hat.com>
To:     VMware Graphics <linux-graphics-maintainer@...are.com>,
        Sinclair Yeh <syeh@...are.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     Vladis Dronov <vdronov@...hat.com>
Subject: [PATCH] drm/vmwgfx: Check check that number of mip levels is above zero in vmw_surface_define_ioctl()

In vmw_surface_define_ioctl(), a num_sizes parameter is assigned a
user-controlled value which is not checked for zero. It is used in
a call to kmalloc() which returns ZERO_SIZE_PTR. Later ZERO_SIZE_PTR
is dereferenced which leads to a GPF and possibly to a kernel panic.
Add the check for zero to avoid this.

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=1435719
Signed-off-by: Vladis Dronov <vdronov@...hat.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
index b445ce9..42840cc 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -716,8 +716,8 @@ int vmw_surface_define_ioctl(struct drm_device *dev, void *data,
 	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 <= 0 ||
+	    num_sizes > DRM_VMW_MAX_SURFACE_FACES * DRM_VMW_MAX_MIP_LEVELS)
 		return -EINVAL;
 
 	size = vmw_user_surface_size + 128 +
-- 
2.9.3