Patch "drm/vc4: Fix NULL pointer dereference in vc4_save_hang_state()" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

drm/vc4: Fix NULL pointer dereference in vc4_save_hang_state()

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-vc4-fix-null-pointer-dereference-in-vc4_save_hang_state.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Boris Brezillon <[email protected]>
Date: Thu, 18 Jan 2018 15:58:21 +0100
Subject: drm/vc4: Fix NULL pointer dereference in vc4_save_hang_state()

From: Boris Brezillon <[email protected]>

commit 17b11b76b87afe9f8be199d7a5f442497133e2b0 upstream.

When saving BOs in the hang state we skip one entry of the kernel_state->bo[] array, thus leaving it to NULL. This leads to a NULL pointer dereference when, later in this function, we iterate over all BOs to check their ->madv state.

---
 drivers/gpu/drm/vc4/vc4_gem.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

@@ -146,7 +146,7 @@ vc4_save_hang_state(struct drm_device *d
 	struct vc4_exec_info *exec[2];
 	struct vc4_bo *bo;
 	unsigned long irqflags;
-	unsigned int i, j, unref_list_count, prev_idx;
+	unsigned int i, j, k, unref_list_count;
 
 	kernel_state = kcalloc(1, sizeof(*kernel_state), GFP_KERNEL);
 	if (!kernel_state)

@@ -182,24 +182,24 @@ vc4_save_hang_state(struct drm_device *d
 		return;
 	}
 
-	prev_idx = 0;
+	k = 0;
 	for (i = 0; i < 2; i++) {
 		if (!exec[i])
 			continue;
 
 		for (j = 0; j < exec[i]->bo_count; j++) {
 			drm_gem_object_get(&exec[i]->bo[j]->base);
-			kernel_state->bo[j + prev_idx] = &exec[i]->bo[j]->base;
+			kernel_state->bo[k++] = &exec[i]->bo[j]->base;
 		}
 
 		list_for_each_entry(bo, &exec[i]->unref_list, unref_head) {
 			drm_gem_object_get(&bo->base.base);
-			kernel_state->bo[j + prev_idx] = &bo->base.base;
-			j++;
+			kernel_state->bo[k++] = &bo->base.base;
 		}
-		prev_idx = j + 1;
 	}
 
+	WARN_ON_ONCE(k != state->bo_count);
+
 	if (exec[0])
 		state->start_bin = exec[0]->ct0ca;
 	if (exec[1])

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/drm-vc4-fix-null-pointer-dereference-in-vc4_save_hang_state.patch