Patch "tipc: fix nametbl deadlock at tipc_nametbl_unsubscribe" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

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

    tipc: fix nametbl deadlock at tipc_nametbl_unsubscribe

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-deadlock-at-tipc_nametbl_unsubscribe.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@vger.kernel.org> know about it.


>From foo@baz Thu Dec 21 09:02:40 CET 2017
From: Ying Xue <ying.xue@windriver.com>
Date: Tue, 21 Mar 2017 10:47:49 +0100
Subject: tipc: fix nametbl deadlock at tipc_nametbl_unsubscribe

From: Ying Xue <ying.xue@windriver.com>


[ Upstream commit 557d054c01da0337ca81de9e9d9206d57245b57e ]

Until now, tipc_nametbl_unsubscribe() is called at subscriptions
reference count cleanup. Usually the subscriptions cleanup is
called at subscription timeout or at subscription cancel or at
subscriber delete.

We have ignored the possibility of this being called from other
locations, which causes deadlock as we try to grab the
tn->nametbl_lock while holding it already.

   CPU1:                             CPU2:
----------                     ----------------
tipc_nametbl_publish
spin_lock_bh(&tn->nametbl_lock)
tipc_nametbl_insert_publ
tipc_nameseq_insert_publ
tipc_subscrp_report_overlap
tipc_subscrp_get
tipc_subscrp_send_event
                             tipc_close_conn
                             tipc_subscrb_release_cb
                             tipc_subscrb_delete
                             tipc_subscrp_put
tipc_subscrp_put
tipc_subscrp_kref_release
tipc_nametbl_unsubscribe
spin_lock_bh(&tn->nametbl_lock)
<<grab nametbl_lock again>>

   CPU1:                              CPU2:
----------                     ----------------
tipc_nametbl_stop
spin_lock_bh(&tn->nametbl_lock)
tipc_purge_publications
tipc_nameseq_remove_publ
tipc_subscrp_report_overlap
tipc_subscrp_get
tipc_subscrp_send_event
                             tipc_close_conn
                             tipc_subscrb_release_cb
                             tipc_subscrb_delete
                             tipc_subscrp_put
tipc_subscrp_put
tipc_subscrp_kref_release
tipc_nametbl_unsubscribe
spin_lock_bh(&tn->nametbl_lock)
<<grab nametbl_lock again>>

In this commit, we advance the calling of tipc_nametbl_unsubscribe()
from the refcount cleanup to the intended callers.

Fixes: d094c4d5f5c7 ("tipc: add subscription refcount to avoid invalid delete")
Reported-by: John Thompson <thompa.atl@gmail.com>
Acked-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/tipc/subscr.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/net/tipc/subscr.c
+++ b/net/tipc/subscr.c
@@ -141,6 +141,11 @@ void tipc_subscrp_report_overlap(struct
 static void tipc_subscrp_timeout(unsigned long data)
 {
 	struct tipc_subscription *sub = (struct tipc_subscription *)data;
+	struct tipc_subscriber *subscriber = sub->subscriber;
+
+	spin_lock_bh(&subscriber->lock);
+	tipc_nametbl_unsubscribe(sub);
+	spin_unlock_bh(&subscriber->lock);
 
 	/* Notify subscriber of timeout */
 	tipc_subscrp_send_event(sub, sub->evt.s.seq.lower, sub->evt.s.seq.upper,
@@ -173,7 +178,6 @@ static void tipc_subscrp_kref_release(st
 	struct tipc_subscriber *subscriber = sub->subscriber;
 
 	spin_lock_bh(&subscriber->lock);
-	tipc_nametbl_unsubscribe(sub);
 	list_del(&sub->subscrp_list);
 	atomic_dec(&tn->subscription_count);
 	spin_unlock_bh(&subscriber->lock);
@@ -205,6 +209,7 @@ static void tipc_subscrb_subscrp_delete(
 		if (s && memcmp(s, &sub->evt.s, sizeof(struct tipc_subscr)))
 			continue;
 
+		tipc_nametbl_unsubscribe(sub);
 		tipc_subscrp_get(sub);
 		spin_unlock_bh(&subscriber->lock);
 		tipc_subscrp_delete(sub);


Patches currently in stable-queue which might be from ying.xue@windriver.com are

queue-4.9/tipc-fix-nametbl-deadlock-at-tipc_nametbl_unsubscribe.patch