| Message ID | 25145358.1155254.1503499382947.JavaMail.zimbra@redhat.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Wed, Aug 23, 2017 at 10:43:02AM -0400, Bob Peterson wrote: > Hi, > > 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(). > > Signed-off-by: Bob Peterson <rpeterso@redhat.com> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Thanks for catching this!
From: Bob Peterson <rpeterso@redhat.com> Date: Wed, 23 Aug 2017 10:43:02 -0400 (EDT) > 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(). > > Signed-off-by: Bob Peterson <rpeterso@redhat.com> Applied and queued up for -stable, thanks.
diff --git a/net/tipc/socket.c b/net/tipc/socket.c index 101e3597338f..d50edd6e0019 100644 --- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -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)); }
Hi, 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(). Signed-off-by: Bob Peterson <rpeterso@redhat.com> ---