I think it makes sense to add a Fixes tag to this:
Fixes: 822cab6150d3 ("drm/nouveau/svm: check for SVM initialized
before migrating")
Reviewed-by: Karol Herbst <kherbst@xxxxxxxxxx>
On Tue, Sep 7, 2021 at 3:20 PM Chenyuan Mi <cymi20@xxxxxxxxxxxx> wrote:
>
> The reference counting issue happens in one exception handling path of
> nouveau_svmm_bind(). When cli->svm.svmm is null, the function forgets
> to decrease the refcount of mm increased by get_task_mm(), causing a
> refcount leak.
>
> Fix this issue by using mmput() to decrease the refcount in the
> exception handling path.
>
> Also, the function forgets to do check against null when get mm
> by get_task_mm().
>
> Fix this issue by adding null check after get mm by get_task_mm().
>
> Signed-off-by: Chenyuan Mi <cymi20@xxxxxxxxxxxx>
> Signed-off-by: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>
> Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
> ---
> drivers/gpu/drm/nouveau/nouveau_svm.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
> index b0c3422cb01f..9985bfde015a 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_svm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
> @@ -162,10 +162,14 @@ nouveau_svmm_bind(struct drm_device *dev, void *data,
> */
>
> mm = get_task_mm(current);
> + if (!mm) {
> + return -EINVAL;
> + }
> mmap_read_lock(mm);
>
> if (!cli->svm.svmm) {
> mmap_read_unlock(mm);
> + mmput(mm);
> return -EINVAL;
> }
>
> --
> 2.17.1
>
