Patch "tipc: Fix tipc_sk_reinit handling of -EAGAIN" has been added to the 4.12-stable tree

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

tipc: Fix tipc_sk_reinit handling of -EAGAIN

to the 4.12-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-tipc_sk_reinit-handling-of-eagain.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Bob Peterson <[email protected]>
Date: Wed, 23 Aug 2017 10:43:02 -0400
Subject: tipc: Fix tipc_sk_reinit handling of -EAGAIN

From: Bob Peterson <[email protected]>

[ Upstream commit 6c7e983b220f89e03286dc70a41c7ef3a8b409df ]

In 9dbbfb0ab6680c6a85609041011484e6658e7d3c function tipc_sk_reinit had additional logic added to loop in the event that function rhashtable_walk_next() returned -EAGAIN. No worries.

However, if rhashtable_walk_start returns -EAGAIN, it does "continue", and therefore skips the call to rhashtable_walk_stop(). That has the effect of calling rcu_read_lock() without its paired call to rcu_read_unlock(). Since rcu_read_lock() may be nested, the problem may not be apparent for a while, especially since resize events may be rare. But the comments to rhashtable_walk_start() state:

* ...Note that we take the RCU lock in all
* cases including when we return an error. So you must always call
* rhashtable_walk_stop to clean up.

This patch replaces the continue with a goto and label to ensure a matching call to rhashtable_walk_stop().

---
 net/tipc/socket.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -2255,8 +2255,8 @@ void tipc_sk_reinit(struct net *net)
 
 	do {
 		tsk = ERR_PTR(rhashtable_walk_start(&iter));
-		if (tsk)
-			continue;
+		if (IS_ERR(tsk))
+			goto walk_stop;
 
 		while ((tsk = rhashtable_walk_next(&iter)) && !IS_ERR(tsk)) {
 			spin_lock_bh(&tsk->sk.sk_lock.slock);

@@ -2265,7 +2265,7 @@ void tipc_sk_reinit(struct net *net)
 			msg_set_orignode(msg, tn->own_addr);
 			spin_unlock_bh(&tsk->sk.sk_lock.slock);
 		}
-
+walk_stop:
 		rhashtable_walk_stop(&iter);
 	} while (tsk == ERR_PTR(-EAGAIN));
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/tipc-fix-tipc_sk_reinit-handling-of-eagain.patch