[PATCH v2] drm/i915: clarify reasoning for the access_ok call
From: Kees Cook
Date: Mon Mar 11 2013 - 17:37:47 EST
This clarifies the comment above the access_ok check so a missing
VERIFY_READ doesn't alarm anyone.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
v2:
- rewrote comment, thanks to Chris Wilson
---
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index bf7ceca..89c4039 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -751,7 +751,11 @@ validate_exec_list(struct drm_i915_gem_exec_object2 *exec,
length = exec[i].relocation_count *
sizeof(struct drm_i915_gem_relocation_entry);
- /* we may also need to update the presumed offsets */
+ /*
+ * We must check that the entire relocation array is safe
+ * to read, but since we may need to update the presumed
+ * offsets during execution, check for full write access.
+ */
if (!access_ok(VERIFY_WRITE, ptr, length))
return -EFAULT;
--
1.7.9.5
--
Kees Cook
Chrome OS Security
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