[Intel-gfx] [PATCH] drm/i915: properly sanity check batch_start_offset

[Matthew Auld]

Check the edge case where batch_start_offset sits exactly on the batch
size.

Testcase: igt/gem_exec_params/invalid-batch-start-offset
Fixes: 0b5372727be3 ("drm/i915/cmdparser: Use cached vmappings")
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 7bb27f382af7..5247de18a3d0 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2714,7 +2714,8 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 		goto err_vma;
 	}
 
-	if (range_overflows_t(u64,
+	if (eb.batch_start_offset == eb.batch->vma->size ||
+	    range_overflows_t(u64,
 			      eb.batch_start_offset, eb.batch_len,
 			      eb.batch->vma->size)) {
 		drm_dbg(&i915->drm, "Attempting to use out-of-bounds batch\n");
-- 
2.20.1