drm/i915: fix integer overflow in i915_gem_execbuffer2()

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@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index ed00f29472a81468f95dd2154eeca1e0b4a7c340..5b6fe317e42c322f17722120cb53b6f9e0c8108e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1322,7 +1322,8 @@ 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;
        }