This is a note to let you know that I've just added the patch titled tipc: fix nametbl_lock soft lockup at node/link events to the 4.9-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: tipc-fix-nametbl_lock-soft-lockup-at-node-link-events.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Jun 15 16:35:05 CEST 2017 From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@xxxxxxxxxxxx> Date: Tue, 24 Jan 2017 13:00:43 +0100 Subject: tipc: fix nametbl_lock soft lockup at node/link events From: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@xxxxxxxxxxxx> [ Upstream commit 93f955aad4bacee5acebad141d1a03cd51f27b4e ] We trigger a soft lockup as we grab nametbl_lock twice if the node has a pending node up/down or link up/down event while: - we process an incoming named message in tipc_named_rcv() and perform an tipc_update_nametbl(). - we have pending backlog items in the name distributor queue during a nametable update using tipc_nametbl_publish() or tipc_nametbl_withdraw(). The following are the call chain associated: tipc_named_rcv() Grabs nametbl_lock tipc_update_nametbl() (publish/withdraw) tipc_node_subscribe()/unsubscribe() tipc_node_write_unlock() << lockup occurs if an outstanding node/link event exits, as we grabs nametbl_lock again >> tipc_nametbl_withdraw() Grab nametbl_lock tipc_named_process_backlog() tipc_update_nametbl() << rest as above >> The function tipc_node_write_unlock(), in addition to releasing the lock processes the outstanding node/link up/down events. To do this, we need to grab the nametbl_lock again leading to the lockup. In this commit we fix the soft lockup by introducing a fast variant of node_unlock(), where we just release the lock. We adapt the node_subscribe()/node_unsubscribe() to use the fast variants. Reported-and-Tested-by: John Thompson <thompa.atl@xxxxxxxxx> Acked-by: Ying Xue <ying.xue@xxxxxxxxxxxxx> Acked-by: Jon Maloy <jon.maloy@xxxxxxxxxxxx> Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@xxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/tipc/node.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -263,6 +263,11 @@ static void tipc_node_write_lock(struct write_lock_bh(&n->lock); } +static void tipc_node_write_unlock_fast(struct tipc_node *n) +{ + write_unlock_bh(&n->lock); +} + static void tipc_node_write_unlock(struct tipc_node *n) { struct net *net = n->net; @@ -417,7 +422,7 @@ void tipc_node_subscribe(struct net *net } tipc_node_write_lock(n); list_add_tail(subscr, &n->publ_list); - tipc_node_write_unlock(n); + tipc_node_write_unlock_fast(n); tipc_node_put(n); } @@ -435,7 +440,7 @@ void tipc_node_unsubscribe(struct net *n } tipc_node_write_lock(n); list_del_init(subscr); - tipc_node_write_unlock(n); + tipc_node_write_unlock_fast(n); tipc_node_put(n); } Patches currently in stable-queue which might be from parthasarathy.bhuvaragan@xxxxxxxxxxxx are queue-4.9/tipc-fix-connection-refcount-error.patch queue-4.9/tipc-fix-nametbl_lock-soft-lockup-at-node-link-events.patch queue-4.9/tipc-ignore-requests-when-the-connection-state-is-not-connected.patch queue-4.9/tipc-add-subscription-refcount-to-avoid-invalid-delete.patch