linux-kernel - [ 111/167] [PATCH] drm/i915: fix integer overflow in i915_gem

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Message-Id: <20120509055045.040760162@decadent.org.uk>
Date:	Wed, 09 May 2012 06:52:20 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Xi Wang <xi.wang@...il.com>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [ 111/167] [PATCH] drm/i915: fix integer overflow in i915_gem_execbuffer2()

3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Xi Wang <xi.wang@...il.com>

commit ed8cd3b2cd61004cab85380c52b1817aca1ca49b upstream.

On 32-bit systems, a large args->buffer_count from userspace via ioctl
may overflow the allocation size, leading to out-of-bounds access.

This vulnerability was introduced in commit 8408c282 ("drm/i915:
First try a normal large kmalloc for the temporary exec buffers").

Signed-off-by: Xi Wang <xi.wang@...il.com>
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index f51a696..7c50e58 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1404,7 +1404,8 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 	struct drm_i915_gem_exec_object2 *exec2_list = NULL;
 	int ret;
 
-	if (args->buffer_count < 1) {
+	if (args->buffer_count < 1 ||
+	    args->buffer_count > UINT_MAX / sizeof(*exec2_list)) {
 		DRM_ERROR("execbuf2 with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}


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