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Subject[PATCH] drm/i915: bounds check execbuffer relocations
It is possible to wrap the counter used to allocate the buffer for
relocation copies. This could lead to heap writing overflows.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Pinkie Pie
Cc: stable@vger.kernel.org
---
drivers/gpu/drm/i915/i915_gem_execbuffer.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 752e399..62eaa99 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -585,7 +585,8 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
struct drm_i915_gem_object *obj;
bool need_relocs;
int *reloc_offset;
- int i, total, ret;
+ int ret;
+ unsigned int i, total;
int count = args->buffer_count;

/* We may process another execbuffer during the unlock... */
@@ -600,8 +601,13 @@ i915_gem_execbuffer_relocate_slow(struct drm_device *dev,
mutex_unlock(&dev->struct_mutex);

total = 0;
- for (i = 0; i < count; i++)
+ for (i = 0; i < count; i++) {
+ if (exec[i].relocation_count > UINT_MAX - total) {
+ mutex_lock(&dev->struct_mutex);
+ return -ENOMEM;
+ }
total += exec[i].relocation_count;
+ }

reloc_offset = drm_malloc_ab(count, sizeof(*reloc_offset));
reloc = drm_malloc_ab(total, sizeof(*reloc));
--
1.7.9.5

--
Kees Cook
Chrome OS Security


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