[PATCH] drm: make drm_dp_add_payload_part2 gracefully handle NULL state pointer

Jeff Layton
2023-04-13T11:13:01Z

I've been experiencing some intermittent crashes down in the display
driver code. The symptoms are ususally a line like this in dmesg:

amdgpu 0000:30:00.0: [drm] Failed to create MST payload for port 000000006d3a3885: -5

...followed by an Oops due to a NULL pointer dereference.

The real bug is probably in the caller of this function, which is
passing it a NULL state pointer, but this patch at least keeps my
machine from oopsing when this occurs.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=2184855
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
drivers/gpu/drm/display/drm_dp_mst_topology.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index 38dab76ae69e..87ad406c50f9 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3404,7 +3404,8 @@ int drm_dp_add_payload_part2(struct drm_dp_mst_topology_mgr *mgr,

/* Skip failed payloads */
if (payload->vc_start_slot == -1) {
- drm_dbg_kms(state->dev, "Part 1 of payload creation for %s failed, skipping part 2\n",
+ drm_dbg_kms(state ? state->dev : NULL,
+ "Part 1 of payload creation for %s failed, skipping part 2\n",
payload->port->connector->name);
return -EIO;
}
--
2.39.2