[Intel-gfx] [PATCH] CHROMIUM: drm/i915: bounds check execbuffer relocations

[james.ausmus at intel.com]

From: Kees Cook <keescook at chromium.org>

It is possible to wrap the counter used to allocate the buffer for
relocation copies. This could lead to heap writing overflows.

BUG=chromium-os:39733
TEST=link build, PoC fails

[sending upstream]

Change-Id: Ifdd4ae846042852a4462d70cfa3c3b84d5a9d133
Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/45118
Reviewed-by: Jorge Lucangeli Obes <jorgelo at chromium.org>
Reviewed-by: Stéphane Marchesin <marcheu at chromium.org>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 26d08bb..b23d6cd 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -706,6 +706,7 @@ validate_exec_list(struct drm_i915_gem_exec_object2 *exec,
 		   int count)
 {
 	int i;
+	int total = 0;
 
 	for (i = 0; i < count; i++) {
 		char __user *ptr = (char __user *)(uintptr_t)exec[i].relocs_ptr;
@@ -715,6 +716,9 @@ validate_exec_list(struct drm_i915_gem_exec_object2 *exec,
 		if (exec[i].relocation_count >
 		    INT_MAX / sizeof(struct drm_i915_gem_relocation_entry))
 			return -EINVAL;
+		if (exec[i].relocation_count > INT_MAX - total)
+			return -EINVAL;
+		total += exec[i].relocation_count;
 
 		length = exec[i].relocation_count *
 			sizeof(struct drm_i915_gem_relocation_entry);
-- 
1.8.3.2