linux-kernel - [PATCH 3.16 105/178] drm/vmwgfx: avoid calling vzalloc with a 0 size in vmw_get_cap_3d

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Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Sinclair Yeh" <syeh@...are.com>,
        "Murray McAllister" <murray.mcallister@...omniasec.com>
Subject: [PATCH 3.16 105/178] drm/vmwgfx: avoid calling vzalloc with a 0
 size in vmw_get_cap_3d_ioctl()

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

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

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

commit 63774069d9527a1aeaa4aa20e929ef5e8e9ecc38 upstream.

In vmw_get_cap_3d_ioctl(), a user can supply 0 for a size that is
used in vzalloc(). This eventually calls dump_stack() (in warn_alloc()),
which can leak useful addresses to dmesg.

Add check to avoid a size of 0.

Signed-off-by: Murray McAllister <murray.mcallister@...omniasec.com>
Reviewed-by: Sinclair Yeh <syeh@...are.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ioctl.c
@@ -161,7 +161,7 @@ int vmw_get_cap_3d_ioctl(struct drm_devi
 	bool gb_objects = !!(dev_priv->capabilities & SVGA_CAP_GBOBJECTS);
 	struct vmw_fpriv *vmw_fp = vmw_fpriv(file_priv);
 
-	if (unlikely(arg->pad64 != 0)) {
+	if (unlikely(arg->pad64 != 0 || arg->max_size == 0)) {
 		DRM_ERROR("Illegal GET_3D_CAP argument.\n");
 		return -EINVAL;
 	}