From: jsg <jsg@openbsd.org>
Date: Mon, 5 Sep 2022 14:09:09 +0000 (+0000)
Subject: drm/amd/display: Avoid MPC infinite loop
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=d97021bf0bf19401709587d93c602c9108822b8f;p=openbsd

drm/amd/display: Avoid MPC infinite loop

From Josip Pavic
0c8abeceee0f58ad3fdc66e1de0c0e02b962653b in linux 5.15.y/5.15.65
8de297dc046c180651c0500f8611663ae1c3828a in mainline linux
---

diff --git a/sys/dev/pci/drm/amd/display/dc/dcn10/dcn10_mpc.c b/sys/dev/pci/drm/amd/display/dc/dcn10/dcn10_mpc.c
index 11019c2c62c..8192f1967e9 100644
--- a/sys/dev/pci/drm/amd/display/dc/dcn10/dcn10_mpc.c
+++ b/sys/dev/pci/drm/amd/display/dc/dcn10/dcn10_mpc.c
@@ -126,6 +126,12 @@ struct mpcc *mpc1_get_mpcc_for_dpp(struct mpc_tree *tree, int dpp_id)
 	while (tmp_mpcc != NULL) {
 		if (tmp_mpcc->dpp_id == dpp_id)
 			return tmp_mpcc;
+
+		/* avoid circular linked list */
+		ASSERT(tmp_mpcc != tmp_mpcc->mpcc_bot);
+		if (tmp_mpcc == tmp_mpcc->mpcc_bot)
+			break;
+
 		tmp_mpcc = tmp_mpcc->mpcc_bot;
 	}
 	return NULL;
diff --git a/sys/dev/pci/drm/amd/display/dc/dcn20/dcn20_mpc.c b/sys/dev/pci/drm/amd/display/dc/dcn20/dcn20_mpc.c
index 947eb0df3f1..142fc0a3a53 100644
--- a/sys/dev/pci/drm/amd/display/dc/dcn20/dcn20_mpc.c
+++ b/sys/dev/pci/drm/amd/display/dc/dcn20/dcn20_mpc.c
@@ -532,6 +532,12 @@ struct mpcc *mpc2_get_mpcc_for_dpp(struct mpc_tree *tree, int dpp_id)
 	while (tmp_mpcc != NULL) {
 		if (tmp_mpcc->dpp_id == 0xf || tmp_mpcc->dpp_id == dpp_id)
 			return tmp_mpcc;
+
+		/* avoid circular linked list */
+		ASSERT(tmp_mpcc != tmp_mpcc->mpcc_bot);
+		if (tmp_mpcc == tmp_mpcc->mpcc_bot)
+			break;
+
 		tmp_mpcc = tmp_mpcc->mpcc_bot;
 	}
 	return NULL;