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Subject[PATCH] drm: Check for connector->state NULL in drm_atomic_add_affected_connectors
Date
On a system I'm doing development on I found a crash.  The crawl looked
like:

PC is at drm_atomic_add_affected_connectors+0x98/0xe8
...
drm_atomic_add_affected_connectors from __drm_atomic_helper_set_config+0x218/0x344
__drm_atomic_helper_set_config from restore_fbdev_mode+0x108/0x250
restore_fbdev_mode from drm_fb_helper_restore_fbdev_mode_unlocked+0x3c/0x80
drm_fb_helper_restore_fbdev_mode_unlocked from rockchip_drm_lastclose+0x1c/0x20
rockchip_drm_lastclose from drm_lastclose+0x4c/0x104
drm_lastclose from drm_release+0x424/0x47c
drm_release from __fput+0xf8/0x1d4
__fput from ____fput+0x18/0x1c
____fput from task_work_run+0xa8/0xbc
task_work_run from do_exit+0x448/0x91c
do_exit from do_group_exit+0x5c/0xcc
do_group_exit from get_signal+0x4dc/0x57c
get_signal from do_signal+0x9c/0x3b4
do_signal from do_work_pending+0x60/0xb8
do_work_pending from slow_work_pending+0xc/0x20

I found that I could fix the crash by checking connector->state against
NULL. This isn't code I'm familiar with and I didn't dig too deep, so
I'd appreciate any opinions about whether this is a sane thing to do.
Note that I don't actually have graphics up on my system at the moment,
so perhaps this is all just a symptom of the strange state I'm in.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---
drivers/gpu/drm/drm_atomic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 8fb469c4e4b8..3377d7ddc6d1 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1147,7 +1147,7 @@ drm_atomic_add_affected_connectors(struct drm_atomic_state *state,
* current configuration.
*/
drm_for_each_connector(connector, state->dev) {
- if (connector->state->crtc != crtc)
+ if (!connector->state || connector->state->crtc != crtc)
continue;

conn_state = drm_atomic_get_connector_state(state, connector);
--
2.7.0.rc3.207.g0ac5344
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