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 6.1-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-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 7b03d5eca73859a73a9deec46eac173dd453279a 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 9b8eaebce254..f2dd846ff903 100644 --- a/net/hsr/hsr_framereg.c +++ b/net/hsr/hsr_framereg.c @@ -366,9 +366,12 @@ 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: /* Push back here */ @@ -539,9 +542,12 @@ 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 bdbb8c822ba1..b5f902397bf1 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; };