Am 27.10.22 um 00:46 schrieb Dmitry Osipenko:
The drm_gem_vunmap() will crash with a NULL dereference if the passed
object pointer is NULL. It wasn't a problem before we added the locking
support to drm_gem_vunmap function because the mapping argument was always
NULL together with the object. Make drm_gem_vunmap() functions to handle
the NULL pointers better.
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Link: https://lore.kernel.org/dri-devel/Y1kFEGxT8MVlf32V@kili/
Fixes: 79e2cf2e7a19 ("drm/gem: Take reservation lock for vmap/vunmap operations")
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
drivers/gpu/drm/drm_gem.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index b8db675e7fb5..ee0a246ff4ac 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1175,11 +1175,11 @@ EXPORT_SYMBOL(drm_gem_vmap);
void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map)
{
- dma_resv_assert_held(obj->resv);
-
- if (iosys_map_is_null(map))
+ if (!obj || iosys_map_is_null(map))
return;
I'm not very keen about that. Calling a function with all parameters
NULL doesn't make much sense and is clearly a coding error. Hiding that
somehow doesn't help but rather makes things worse.
The only execption to that are things like kfree() or *_put() which work
with the lifetime of objects.
Why is the static checker complaining about that in the first place?
Regards,
Christian.
+ dma_resv_assert_held(obj->resv);
+
if (obj->funcs->vunmap)
obj->funcs->vunmap(obj, map);
@@ -1202,6 +1202,9 @@ EXPORT_SYMBOL(drm_gem_vmap_unlocked);
void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map)
{
+ if (!obj || iosys_map_is_null(map))
+ return;
+
dma_resv_lock(obj->resv, NULL);
drm_gem_vunmap(obj, map);
dma_resv_unlock(obj->resv);
