[PATCH AUTOSEL 4.9 21/98] tipc: Fix tipc_sk_reinit handling of -EAGAIN

From: Sasha Levin
Date: Thu Oct 25 2018 - 10:15:02 EST

From: Bob Peterson <rpeterso@xxxxxxxxxx>

[ 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().

Signed-off-by: Bob Peterson <rpeterso@xxxxxxxxxx>
Acked-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
net/tipc/socket.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 25bc5c30d7fb..9d3f047305ce 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -2277,8 +2277,8 @@ 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)) {
@@ -2287,7 +2287,7 @@ void tipc_sk_reinit(struct net *net)
msg_set_orignode(msg, tn->own_addr);
} while (tsk == ERR_PTR(-EAGAIN));