| Message ID | 20221026224640.7542-3-dmitry.osipenko@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fixes for dma-buf locking issues found by Smatch | expand |
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@oracle.com> > 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@collabora.com> > --- > 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);
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@oracle.com> > > 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@collabora.com> > > --- > > 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
Am 27.10.22 um 09:28 schrieb Dan Carpenter: > 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@oracle.com> >>> Link: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fdri-devel%2FY1kFEGxT8MVlf32V%40kili%2F&data=05%7C01%7Cchristian.koenig%40amd.com%7C50d3b7e10eca4c7fb72108dab7ecd646%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638024525139985844%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=ET0TRHscb1bQVVHgBkmYvTQyV2Q6WqcMC83LDlrY5ZM%3D&reserved=0 Fixes: >>> 79e2cf2e7a19 ("drm/gem: Take reservation lock for vmap/vunmap >>> operations") >>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com> >>> --- >>> 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) Well than rather modify drm_client_buffer_delete() instead. Calling drm_gem_vunmap() with obj NULL is certainly not a good idea if we even check that for drm_gem_object_put(). Interesting that the static checkers complain about that :) Regards, Christian. > > regards, > dan carpenter >
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; + 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);
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@oracle.com> 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@collabora.com> --- drivers/gpu/drm/drm_gem.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)