On Thu, Oct 27, 2022 at 08:17:31AM +0200, Christian König wrote: > > > 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? > drivers/gpu/drm/drm_client.c:240 drm_client_buffer_delete() warn: variable dereferenced before check 'buffer->gem' (see line 238) regards, dan carpenter
