If the MST topology is removed during the reception of an MST down reply
or MST up request sideband message, the
drm_dp_mst_topology_mgr::up_req_recv/down_rep_recv states could be reset
from one thread via drm_dp_mst_topology_mgr_set_mst(false), racing with
the reading/parsing of the message from another thread via
drm_dp_mst_handle_down_rep() or drm_dp_mst_handle_up_req(). The race is
possible since the reader/parser doesn't hold any lock while accessing
the reception state. This in turn can lead to a memory corruption in the
reader/parser as described by commit bd2fccac61b4 ("drm/dp_mst: Fix MST
sideband message body length check").
Fix the above by resetting the message reception state if needed before
reading/parsing a message. Another solution would be to hold the
drm_dp_mst_topology_mgr::lock for the whole duration of the message
reception/parsing in drm_dp_mst_handle_down_rep() and
drm_dp_mst_handle_up_req(), however this would require a bigger change.
Since the fix is also needed for stable, opting for the simpler solution
in this patch.
Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 1d082618bbf3 ("drm/display/dp_mst: Fix down/up message handling after sink disconnect")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13056
Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20241203160223.2926014-2-imre.deak@xxxxxxxxx
diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index e6ee180815b2..1475aa95ab6b 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3700,8 +3700,7 @@ int drm_dp_mst_topology_mgr_set_mst(struct drm_dp_mst_topology_mgr *mgr, bool ms
ret = 0;
mgr->payload_id_table_cleared = false;
- memset(&mgr->down_rep_recv, 0, sizeof(mgr->down_rep_recv));
- memset(&mgr->up_req_recv, 0, sizeof(mgr->up_req_recv));
+ mgr->reset_rx_state = true;
}
out_unlock:
@@ -3859,6 +3858,11 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
}
EXPORT_SYMBOL(drm_dp_mst_topology_mgr_resume);
+static void reset_msg_rx_state(struct drm_dp_sideband_msg_rx *msg)
+{
+ memset(msg, 0, sizeof(*msg));
+}
+
static bool
drm_dp_get_one_sb_msg(struct drm_dp_mst_topology_mgr *mgr, bool up,
struct drm_dp_mst_branch **mstb)
@@ -4141,6 +4145,17 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
return 0;
}
+static void update_msg_rx_state(struct drm_dp_mst_topology_mgr *mgr)
+{
+ mutex_lock(&mgr->lock);
+ if (mgr->reset_rx_state) {
+ mgr->reset_rx_state = false;
+ reset_msg_rx_state(&mgr->down_rep_recv);
+ reset_msg_rx_state(&mgr->up_req_recv);
+ }
+ mutex_unlock(&mgr->lock);
+}
+
/**
* drm_dp_mst_hpd_irq_handle_event() - MST hotplug IRQ handle MST event
* @mgr: manager to notify irq for.
@@ -4175,6 +4190,8 @@ int drm_dp_mst_hpd_irq_handle_event(struct drm_dp_mst_topology_mgr *mgr, const u
*handled = true;
}
+ update_msg_rx_state(mgr);
+
if (esi[1] & DP_DOWN_REP_MSG_RDY) {
ret = drm_dp_mst_handle_down_rep(mgr);
*handled = true;
diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h
index f6a1cbb0f600..a80ba457a858 100644
--- a/include/drm/display/drm_dp_mst_helper.h
+++ b/include/drm/display/drm_dp_mst_helper.h
@@ -699,6 +699,13 @@ struct drm_dp_mst_topology_mgr {
*/
bool payload_id_table_cleared : 1;
+ /**
+ * @reset_rx_state: The down request's reply and up request message
+ * receiver state must be reset, after the topology manager got
+ * removed. Protected by @lock.
+ */
+ bool reset_rx_state : 1;
+
/**
* @payload_count: The number of currently active payloads in hardware. This value is only
* intended to be used internally by MST helpers for payload tracking, and is only safe to
