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

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

From: Xi Wang <[email protected]>

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 <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1353,7 +1353,8 @@ i915_gem_execbuffer2(struct drm_device *
        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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