net: bridge: mst: pass vlan group directly to br_mst_vlan_set_state

jira LE-1907
cve CVE-2024-36979
Rebuild_History Non-Buildable kernel-4.18.0-553.16.1.el8_10
commit-author Nikolay Aleksandrov <[email protected]>
commit 36c9293

Pass the already obtained vlan group pointer to br_mst_vlan_set_state()
instead of dereferencing it again. Each caller has already correctly
dereferenced it for their context. This change is required for the
following suspicious RCU dereference fix. No functional changes
intended.

Fixes: 3a7c166 ("net: bridge: mst: fix vlan use-after-free")
	Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=9bbe2de1bc9d470eb5fe
	Signed-off-by: Nikolay Aleksandrov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
	Signed-off-by: Jakub Kicinski <[email protected]>
(cherry picked from commit 36c9293)
	Signed-off-by: Jonathan Maple <[email protected]>

Author: PlaidCat

net/bridge/br_mst.c

@@ -73,11 +73,10 @@ int br_mst_get_state(const struct net_device *dev, u16 msti, u8 *state)
 }
 EXPORT_SYMBOL_GPL(br_mst_get_state);
 
-static void br_mst_vlan_set_state(struct net_bridge_port *p, struct net_bridge_vlan *v,
+static void br_mst_vlan_set_state(struct net_bridge_vlan_group *vg,
+				  struct net_bridge_vlan *v,
 				  u8 state)
 {
-	struct net_bridge_vlan_group *vg = nbp_vlan_group(p);
-
 	if (br_vlan_get_state(v) == state)
 		return;
 
@@ -121,7 +120,7 @@ int br_mst_set_state(struct net_bridge_port *p, u16 msti, u8 state,
 		if (v->brvlan->msti != msti)
 			continue;
 
-		br_mst_vlan_set_state(p, v, state);
+		br_mst_vlan_set_state(vg, v, state);
 	}
 
 out:
@@ -140,13 +139,13 @@ static void br_mst_vlan_sync_state(struct net_bridge_vlan *pv, u16 msti)
 		 * it.
 		 */
 		if (v != pv && v->brvlan->msti == msti) {
-			br_mst_vlan_set_state(pv->port, pv, v->state);
+			br_mst_vlan_set_state(vg, pv, v->state);
 			return;
 		}
 	}
 
 	/* Otherwise, start out in a new MSTI with all ports disabled. */
-	return br_mst_vlan_set_state(pv->port, pv, BR_STATE_DISABLED);
+	return br_mst_vlan_set_state(vg, pv, BR_STATE_DISABLED);
 }
 
 int br_mst_vlan_set_msti(struct net_bridge_vlan *mv, u16 msti)