[patch 2/4] drm/qxl: potential NULL dereference in apply_reloc()

[Dan Carpenter]

qxl_bo_kmap_atomic_page() can fail.  I think the user controls
->dst_offset so this can be used to corrupt memory.

Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

diff --git a/drivers/gpu/drm/qxl/qxl_ioctl.c b/drivers/gpu/drm/qxl/qxl_ioctl.c
index eda6f30..b2db482 100644
--- a/drivers/gpu/drm/qxl/qxl_ioctl.c
+++ b/drivers/gpu/drm/qxl/qxl_ioctl.c
@@ -86,6 +86,8 @@ apply_reloc(struct qxl_device *qdev, struct qxl_reloc_info *info)
 {
 	void *reloc_page;
 	reloc_page = qxl_bo_kmap_atomic_page(qdev, info->dst_bo, info->dst_offset & PAGE_MASK);
+	if (!reloc_page)
+		return;
 	*(uint64_t *)(reloc_page + (info->dst_offset & ~PAGE_MASK)) = qxl_bo_physical_address(qdev,
 											      info->src_bo,
 											      info->src_offset);