[AMD Official Use Only - Internal Distribution Only]
Thanks for the catch,
Reviewed-by: Mikita Lipski <mikita.lip...@amd.com>
From: Wayne Lin <wayne....@amd.com>
Sent: Wednesday, December 25, 2019 9:31 PM
To: dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>;
amd-...@lists.freedesktop.org <amd-...@lists.freedesktop.org>
Cc: ly...@redhat.com <ly...@redhat.com>; Kazlauskas, Nicholas
<nicholas.kazlaus...@amd.com>; Wentland, Harry <harry.wentl...@amd.com>;
Lipski, Mikita <mikita.lip...@amd.com>; Zuo, Jerry <jerry....@amd.com>;
sta...@vger.kernel.org <sta...@vger.kernel.org>;
Lin, Wayne <wayne....@amd.com>
Subject: [PATCH] drm/dp_mst: Avoid NULL pointer dereference
[Why]
Found kernel NULL pointer dereference under the below situation:
src — HDMI_Monitor src — HDMI_Monitor
e.g.: \ =>
MSTB — MSTB (unplug) MSTB — MSTB
When display 1 HDMI and 2 DP daisy chain monitors, unplugging the dp
cable connected to source causes kernel NULL pointer dereference at
drm_dp_mst_atomic_check_bw_limit(). When calculating pbn_limit, if
branch is null, accessing "&branch->ports" causes the problem.
[How]
Judge branch is null or not at the beginning. If it is null, return 0.
Signed-off-by: Wayne Lin <wayne....@amd.com>
Cc: sta...@vger.kernel.org
---
drivers/gpu/drm/drm_dp_mst_topology.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
b/drivers/gpu/drm/drm_dp_mst_topology.c
index 7d2d31eaf003..a6473e3ab448 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4707,6 +4707,9 @@ int drm_dp_mst_atomic_check_bw_limit(struct
drm_dp_mst_branch *branch,
struct drm_dp_vcpi_allocation *vcpi;
int pbn_limit = 0, pbn_used = 0;
+ if (!branch)
+ return 0;
+
list_for_each_entry(port, &branch->ports, next) {
if (port->mstb)
if (drm_dp_mst_atomic_check_bw_limit(port->mstb,
mst_state))
--
2.17.1
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