[PATCH 4.9 012/108] tipc: Fix tipc_sk_reinit race conditions

Greg Kroah-Hartman
2017-06-15T17:57:05Z

From: Herbert Xu <herbert@gondor.apana.org.au>

[ Upstream commit 9dbbfb0ab6680c6a85609041011484e6658e7d3c ]

There are two problems with the function tipc_sk_reinit. Firstly
it's doing a manual walk over an rhashtable. This is broken as
an rhashtable can be resized and if you manually walk over it
during a resize then you may miss entries.

Secondly it's missing memory barriers as previously the code used
spinlocks which provide the barriers implicitly.

This patch fixes both problems.

Fixes: 07f6c4bc048a ("tipc: convert tipc reference table to...")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ying Xue <ying.xue@windriver.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/net.c | 4 ++++
net/tipc/socket.c | 30 +++++++++++++++++++-----------
2 files changed, 23 insertions(+), 11 deletions(-)

--- a/net/tipc/net.c
+++ b/net/tipc/net.c
@@ -110,6 +110,10 @@ int tipc_net_start(struct net *net, u32
char addr_string[16];

tn->own_addr = addr;
+
+ /* Ensure that the new address is visible before we reinit. */
+ smp_mb();
+
tipc_named_reinit(net);
tipc_sk_reinit(net);

--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -335,8 +335,6 @@ static int tipc_sk_create(struct net *ne
INIT_LIST_HEAD(&tsk->publications);
msg = &tsk->phdr;
tn = net_generic(sock_net(sk), tipc_net_id);
- tipc_msg_init(tn->own_addr, msg, TIPC_LOW_IMPORTANCE, TIPC_NAMED_MSG,
- NAMED_H_SIZE, 0);

/* Finish initializing socket data structures */
sock->ops = ops;
@@ -346,6 +344,13 @@ static int tipc_sk_create(struct net *ne
pr_warn("Socket create failed; port number exhausted\n");
return -EINVAL;
}
+
+ /* Ensure tsk is visible before we read own_addr. */
+ smp_mb();
+
+ tipc_msg_init(tn->own_addr, msg, TIPC_LOW_IMPORTANCE, TIPC_NAMED_MSG,
+ NAMED_H_SIZE, 0);
+
msg_set_origport(msg, tsk->portid);
setup_timer(&sk->sk_timer, tipc_sk_timeout, (unsigned long)tsk);
sk->sk_backlog_rcv = tipc_backlog_rcv;
@@ -2264,24 +2269,27 @@ static int tipc_sk_withdraw(struct tipc_
void tipc_sk_reinit(struct net *net)
{
struct tipc_net *tn = net_generic(net, tipc_net_id);
- const struct bucket_table *tbl;
- struct rhash_head *pos;
+ struct rhashtable_iter iter;
struct tipc_sock *tsk;
struct tipc_msg *msg;
- int i;

- rcu_read_lock();
- tbl = rht_dereference_rcu((&tn->sk_rht)->tbl, &tn->sk_rht);
- for (i = 0; i < tbl->size; i++) {
- rht_for_each_entry_rcu(tsk, pos, tbl, i, node) {
+ rhashtable_walk_enter(&tn->sk_rht, &iter);
+
+ do {
+ tsk = ERR_PTR(rhashtable_walk_start(&iter));
+ if (tsk)
+ continue;
+
+ while ((tsk = rhashtable_walk_next(&iter)) && !IS_ERR(tsk)) {
spin_lock_bh(&tsk->sk.sk_lock.slock);
msg = &tsk->phdr;
msg_set_prevnode(msg, tn->own_addr);
msg_set_orignode(msg, tn->own_addr);
spin_unlock_bh(&tsk->sk.sk_lock.slock);
}
- }
- rcu_read_unlock();
+
+ rhashtable_walk_stop(&iter);
+ } while (tsk == ERR_PTR(-EAGAIN));
}

static struct tipc_sock *tipc_sk_lookup(struct net *net, u32 portid)