When re-adding a bridge that was previously removed, drm_bridge_add()
drops it from bridge_lingering_list without holding bridge_lock.
Both bridge_list and bridge_lingering_list are protected by bridge_lock,
as they are concurrently modified by drm_bridge_remove() and
__drm_bridge_free(), and walked by the debugfs 'bridges' file. Running
the list_empty() test and the list_del_init() outside of the lock may
therefore corrupt either list.
Perform both under bridge_lock.
Fixes: 17805a15d175 ("drm/bridge: add list of removed refcounted bridges")
Reported-by: Sashiko <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Cristian Ciocaltea <[email protected]>
---
drivers/gpu/drm/drm_bridge.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index afaae272347c..2c457ad74f3b 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -454,8 +454,10 @@ void drm_bridge_add(struct drm_bridge *bridge)
* in bridge_lingering_list. Remove it or bridge_lingering_list will be
* corrupted when adding this bridge to bridge_list below.
*/
+ mutex_lock(&bridge_lock);
if (!list_empty(&bridge->list))
list_del_init(&bridge->list);
+ mutex_unlock(&bridge_lock);
mutex_init(&bridge->hpd_state_mutex);
mutex_init(&bridge->hpd_mutex);
--
2.55.0
