diff options
| author | Rob Clark <robdclark@chromium.org> | 2022-11-30 10:57:48 -0800 |
|---|---|---|
| committer | Javier Martinez Canillas <javierm@redhat.com> | 2022-12-04 18:56:53 +0100 |
| commit | 09bf649a74573cb596e211418a4f8008f265c5a9 (patch) | |
| tree | 5ba072d14eb9fa8c6e4a55b0d1e0f475454895ed /drivers/gpu | |
| parent | 24013314be6ee4ee456114a671e9fa3461323de8 (diff) | |
drm/shmem-helper: Avoid vm_open error paths
vm_open() is not allowed to fail. Fortunately we are guaranteed that
the pages are already pinned, thanks to the initial mmap which is now
being cloned into a forked process, and only need to increment the
refcnt. So just increment it directly. Previously if a signal was
delivered at the wrong time to the forking process, the
mutex_lock_interruptible() could fail resulting in the pages_use_count
not being incremented.
Fixes: 2194a63a818d ("drm: Add library for shmem backed GEM objects")
Cc: stable@vger.kernel.org
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221130185748.357410-3-robdclark@gmail.com
Diffstat (limited to 'drivers/gpu')
| -rw-r--r-- | drivers/gpu/drm/drm_gem_shmem_helper.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 3b7b71391a4c..b602cd72a120 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -571,12 +571,20 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma) { struct drm_gem_object *obj = vma->vm_private_data; struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); - int ret; WARN_ON(shmem->base.import_attach); - ret = drm_gem_shmem_get_pages(shmem); - WARN_ON_ONCE(ret != 0); + mutex_lock(&shmem->pages_lock); + + /* + * We should have already pinned the pages when the buffer was first + * mmap'd, vm_open() just grabs an additional reference for the new + * mm the vma is getting copied into (ie. on fork()). + */ + if (!WARN_ON_ONCE(!shmem->pages_use_count)) + shmem->pages_use_count++; + + mutex_unlock(&shmem->pages_lock); drm_gem_vm_open(vma); } |