drm/i915: Don't touch NULL sg on i915_gem_object_get_pages_gtt() error

commit 2420489bcb8910188578acc0c11c75445c2e4b92 upstream.

On the DMA mapping error path, sg may be NULL (it has already been
marked as the last scatterlist entry), and we should avoid dereferencing
it again.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: e227330223a7 ("drm/i915: avoid leaking DMA mappings")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161114112930.2033-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
(cherry picked from commit b17993b7b29612369270567643bcff814f4b3d7f)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a77ce9983f69c9965725f806a008fc06a129935f..b8e3854a1f2093bc3612a0bf2c4119626c37a8e6 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2540,7 +2540,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
                        page = shmem_read_mapping_page(mapping, i);
                        if (IS_ERR(page)) {
                                ret = PTR_ERR(page);
-                               goto err_pages;
+                               goto err_sg;
                        }
                }
 #ifdef CONFIG_SWIOTLB
@@ -2583,8 +2583,9 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
 
        return 0;
 
-err_pages:
+err_sg:
        sg_mark_end(sg);
+err_pages:
        for_each_sgt_page(page, sgt_iter, st)
                put_page(page);
        sg_free_table(st);