Patch "hsr: Avoid double remove of a node." has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    hsr: Avoid double remove of a node.

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     hsr-avoid-double-remove-of-a-node.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fa101dddfc35763673f1e188761776c0dc7a751b
Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Date:   Tue Nov 29 17:48:10 2022 +0100

    hsr: Avoid double remove of a node.
    
    [ Upstream commit 0c74d9f79ec4299365bbe803baa736ae0068179e ]
    
    Due to the hashed-MAC optimisation one problem become visible:
    hsr_handle_sup_frame() walks over the list of available nodes and merges
    two node entries into one if based on the information in the supervision
    both MAC addresses belong to one node. The list-walk happens on a RCU
    protected list and delete operation happens under a lock.
    
    If the supervision arrives on both slave interfaces at the same time
    then this delete operation can occur simultaneously on two CPUs. The
    result is the first-CPU deletes the from the list and the second CPUs
    BUGs while attempting to dereference a poisoned list-entry. This happens
    more likely with the optimisation because a new node for the mac_B entry
    is created once a packet has been received and removed (merged) once the
    supervision frame has been received.
    
    Avoid removing/ cleaning up a hsr_node twice by adding a `removed' field
    which is set to true after the removal and checked before the removal.
    
    Fixes: f266a683a4804 ("net/hsr: Better frame dispatch")
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c
index e31949479305..440788e5b3e2 100644
--- a/net/hsr/hsr_framereg.c
+++ b/net/hsr/hsr_framereg.c
@@ -326,9 +326,12 @@ void hsr_handle_sup_frame(struct hsr_frame_info *frame)
 	node_real->addr_B_port = port_rcv->type;
 
 	spin_lock_bh(&hsr->list_lock);
-	list_del_rcu(&node_curr->mac_list);
+	if (!node_curr->removed) {
+		list_del_rcu(&node_curr->mac_list);
+		node_curr->removed = true;
+		kfree_rcu(node_curr, rcu_head);
+	}
 	spin_unlock_bh(&hsr->list_lock);
-	kfree_rcu(node_curr, rcu_head);
 
 done:
 	/* PRP uses v0 header */
@@ -502,9 +505,12 @@ void hsr_prune_nodes(struct timer_list *t)
 		if (time_is_before_jiffies(timestamp +
 				msecs_to_jiffies(HSR_NODE_FORGET_TIME))) {
 			hsr_nl_nodedown(hsr, node->macaddress_A);
-			list_del_rcu(&node->mac_list);
-			/* Note that we need to free this entry later: */
-			kfree_rcu(node, rcu_head);
+			if (!node->removed) {
+				list_del_rcu(&node->mac_list);
+				node->removed = true;
+				/* Note that we need to free this entry later: */
+				kfree_rcu(node, rcu_head);
+			}
 		}
 	}
 	spin_unlock_bh(&hsr->list_lock);
diff --git a/net/hsr/hsr_framereg.h b/net/hsr/hsr_framereg.h
index d9628e7a5f05..f9c83dc02ca5 100644
--- a/net/hsr/hsr_framereg.h
+++ b/net/hsr/hsr_framereg.h
@@ -80,6 +80,7 @@ struct hsr_node {
 	bool			san_a;
 	bool			san_b;
 	u16			seq_out[HSR_PT_PORTS];
+	bool			removed;
 	struct rcu_head		rcu_head;
 };