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FAILED: patch "[PATCH] drm/dp_mst: Fix resetting msg rx state after topology removal" failed to apply to 5.10-stable tree

PATCH [email protected] 1 participant 1 message Dec 10, 2024

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The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x a6fa67d26de385c3c7a23c1e109a0e23bfda4ec7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024121008-justify-kosher-0e66@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a6fa67d26de385c3c7a23c1e109a0e23bfda4ec7 Mon Sep 17 00:00:00 2001
From: Imre Deak <[email protected]>
Date: Tue, 3 Dec 2024 18:02:17 +0200
Subject: [PATCH] drm/dp_mst: Fix resetting msg rx state after topology removal

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 <[email protected]>
Cc <[email protected]>
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 <[email protected]>
Signed-off-by Imre Deak <[email protected]>
Link https://patchwork.freedesktop.org/patch/msgid/[email protected]
drivers/gpu/drm/display/drm_dp_mst_topology.c +19 -2
index e6ee180815b2..1475aa95ab6b 100644
@@ -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;
include/drm/display/drm_dp_mst_helper.h +7 -0
index f6a1cbb0f600..a80ba457a858 100644
@@ -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