From 28be2405fb753927e18bc1a891617a430b2a0684 Mon Sep 17 00:00:00 2001 From: Desmond Cheong Zhi Xi Date: Sat, 24 Jul 2021 19:18:22 +0800 Subject: drm: use the lookup lock in drm_is_current_master Inside drm_is_current_master, using the outer drm_device.master_mutex to protect reads of drm_file.master makes the function prone to creating lock hierarchy inversions. Instead, we can use the drm_file.master_lookup_lock that sits at the bottom of the lock hierarchy. Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Daniel Vetter Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210724111824.59266-2-desmondcheongzx@gmail.com --- drivers/gpu/drm/drm_auth.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 3a64a6a79ade..5b1d92f5afea 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -63,8 +63,9 @@ static bool drm_is_current_master_locked(struct drm_file *fpriv) { - lockdep_assert_held_once(&fpriv->minor->dev->master_mutex); - + /* Either drm_device.master_mutex or drm_file.master_lookup_lock + * should be held here. + */ return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; } @@ -82,9 +83,9 @@ bool drm_is_current_master(struct drm_file *fpriv) { bool ret; - mutex_lock(&fpriv->minor->dev->master_mutex); + spin_lock(&fpriv->master_lookup_lock); ret = drm_is_current_master_locked(fpriv); - mutex_unlock(&fpriv->minor->dev->master_mutex); + spin_unlock(&fpriv->master_lookup_lock); return ret; } -- cgit v1.2.3