[PATCH v2] dma-buf: fix an error pointer vs NULL bug

[Christian König]

Am 06.07.23 um 14:37 schrieb Dan Carpenter:
> Smatch detected potential error pointer dereference.
>
>      drivers/gpu/drm/drm_syncobj.c:888 drm_syncobj_transfer_to_timeline()
>      error: 'fence' dereferencing possible ERR_PTR()
>
> The error pointer comes from dma_fence_allocate_private_stub().  One
> caller expected error pointers and one expected NULL pointers.  Change
> it to return NULL and update the caller which expected error pointers,
> drm_syncobj_assign_null_handle(), to check for NULL instead.
>
> Fixes: f781f661e8c9 ("dma-buf: keep the signaling time of merged fences v3")
> Signed-off-by: Dan Carpenter <dan.carpenter at linaro.org>

Reviewed-by: Christian König <christian.koenig at amd.com>

Should I push that one to drm-misc-fixes?

Regards,
Christian.

> ---
> v2: Fix it in dma_fence_allocate_private_stub() instead of
>     __dma_fence_unwrap_merge().
>
>
>   drivers/dma-buf/dma-fence.c   | 2 +-
>   drivers/gpu/drm/drm_syncobj.c | 4 ++--
>   2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index ad076f208760..8aa8f8cb7071 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -160,7 +160,7 @@ struct dma_fence *dma_fence_allocate_private_stub(ktime_t timestamp)
>   
>   	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
>   	if (fence == NULL)
> -		return ERR_PTR(-ENOMEM);
> +		return NULL;
>   
>   	dma_fence_init(fence,
>   		       &dma_fence_stub_ops,
> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> index 04589a35eb09..e592c5da70ce 100644
> --- a/drivers/gpu/drm/drm_syncobj.c
> +++ b/drivers/gpu/drm/drm_syncobj.c
> @@ -355,8 +355,8 @@ static int drm_syncobj_assign_null_handle(struct drm_syncobj *syncobj)
>   {
>   	struct dma_fence *fence = dma_fence_allocate_private_stub(ktime_get());
>   
> -	if (IS_ERR(fence))
> -		return PTR_ERR(fence);
> +	if (!fence)
> +		return -ENOMEM;
>   
>   	drm_syncobj_replace_fence(syncobj, fence);
>   	dma_fence_put(fence);