[PATCH] drm/i915: Sanity check incoming ioctl data for a NULL pointer

[Chris Wilson]

In order to prevent a potential NULL deference with hostile userspace,
we need to check whether the ioctl was passed an invalid args pointer.

Reported-by: Tommi Rantala <tt.rantala@xxxxxxxxx>
Link: http://lkml.kernel.org/r/CA+ydwtpuBvbwxbt-tdgPUvj1EU7itmCHo_2B3w13HkD5+jWKow@xxxxxxxxxxxxxx
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 365e41a..9f5602e 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1103,7 +1103,11 @@ i915_gem_execbuffer(struct drm_device *dev, void *data,
 	struct drm_i915_gem_exec_object2 *exec2_list = NULL;
 	int ret, i;
 
-	if (args->buffer_count < 1) {
+	if (args == NULL)
+		return -EINVAL;
+
+	if (args->buffer_count < 1 ||
+	    args->buffer_count > INT_MAX / sizeof(*exec2_list)) {
 		DRM_DEBUG("execbuf with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}
@@ -1182,8 +1186,11 @@ i915_gem_execbuffer2(struct drm_device *dev, void *data,
 	struct drm_i915_gem_exec_object2 *exec2_list = NULL;
 	int ret;
 
+	if (args == NULL)
+		return -EINVAL;
+
 	if (args->buffer_count < 1 ||
-	    args->buffer_count > UINT_MAX / sizeof(*exec2_list)) {
+	    args->buffer_count > INT_MAX / sizeof(*exec2_list)) {
 		DRM_DEBUG("execbuf2 with %d buffers\n", args->buffer_count);
 		return -EINVAL;
 	}
-- 
1.7.10.4

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