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 <[email protected]>
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 <[email protected]>
---
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;
+ 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);
--
2.37.3
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 <[email protected]>
> 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 <[email protected]>
> ---
> 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);
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 <[email protected]>
>>> 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 <[email protected]>
>>> ---
>>> 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
>
On Thu, Oct 27, 2022 at 08:17:31AM +0200, Christian K?nig 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 <[email protected]>
> > 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 <[email protected]>
> > ---
> > 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