Re: [PATCH] drm: Reorder set_property_atomic to avoid returning with an active ww_ctx

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 30-12-2018 om 13:28 schreef Chris Wilson:
> Delay the drm_modeset_acquire_init() until after we check for an
> allocation failure so that we can return immediately upon error without
> having to unwind.
>
> WARNING: lock held when returning to user space!
> 4.20.0+ #174 Not tainted
> ------------------------------------------------
> syz-executor556/8153 is leaving the kernel with locks still held!
> 1 lock held by syz-executor556/8153:
>   #0: 000000005100c85c (crtc_ww_class_acquire){+.+.}, at:
> set_property_atomic+0xb3/0x330 drivers/gpu/drm/drm_mode_object.c:462
>
> Reported-by: syzbot+6ea337c427f5083ebdf2@syzkaller.appspotmail.com
> Fixes: 144a7999d633 ("drm: Handle properties in the core for atomic drivers")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Sean Paul <sean@poorly.run>
> Cc: David Airlie <airlied@linux.ie>
> Cc: <stable@vger.kernel.org> # v4.14+
> ---
>  drivers/gpu/drm/drm_mode_object.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
> index bb1dd46496cd..a9005c1c2384 100644
> --- a/drivers/gpu/drm/drm_mode_object.c
> +++ b/drivers/gpu/drm/drm_mode_object.c
> @@ -459,12 +459,13 @@ static int set_property_atomic(struct drm_mode_object *obj,
>  	struct drm_modeset_acquire_ctx ctx;
>  	int ret;
>  
> -	drm_modeset_acquire_init(&ctx, 0);
> -
>  	state = drm_atomic_state_alloc(dev);
>  	if (!state)
>  		return -ENOMEM;
> +
> +	drm_modeset_acquire_init(&ctx, 0);
>  	state->acquire_ctx = &ctx;
> +
>  retry:
>  	if (prop == state->dev->mode_config.dpms_property) {
>  		if (obj->type != DRM_MODE_OBJECT_CONNECTOR) {

Woops only now see you did the same.. :)

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>