Re: [PATCH v2 2/2] drm/client: Prevent NULL dereference in drm_client_buffer_delete()

Christian König
2022-11-02T09:19:22Z

Am 30.10.22 um 16:44 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_client_buffer_delete() to check
> whether GEM is NULL before trying to unmap the GEM, it will happen on
> framebuffer creation error.
>
> 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>

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

> ---
> drivers/gpu/drm/drm_client.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index 38e1be991caa..fd67efe37c63 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -235,10 +235,10 @@ static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
> {
> struct drm_device *dev = buffer->client->dev;
>
> - drm_gem_vunmap_unlocked(buffer->gem, &buffer->map);
> -
> - if (buffer->gem)
> + if (buffer->gem) {
> + drm_gem_vunmap_unlocked(buffer->gem, &buffer->map);
> drm_gem_object_put(buffer->gem);
> + }
>
> if (buffer->handle)
> drm_mode_destroy_dumb(dev, buffer->handle, buffer->client->file);