From 4e27762417669cb459971635be550eb7b5598286 Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Fri, 18 Sep 2015 19:16:50 +0800 Subject: netlink: Fix autobind race condition that leads to zero port ID [ Upstream commit 1f770c0a09da855a2b51af6d19de97fb955eca85 ] The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("netlink: Reset portid after netlink_insert failure") introduced a race condition where if two threads try to autobind the same socket one of them may end up with a zero port ID. This led to kernel deadlocks that were observed by multiple people. This patch reverts that commit and instead fixes it by introducing a separte rhash_portid variable so that the real portid is only set after the socket has been successfully hashed. Fixes: c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure") Reported-by: Tejun Heo Reported-by: Linus Torvalds Signed-off-by: Herbert Xu Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/netlink/af_netlink.c | 11 ++++++----- net/netlink/af_netlink.h | 1 + 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 85aeaf27f1b5..4753dc083423 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1017,7 +1017,7 @@ static inline int netlink_compare(struct rhashtable_compare_arg *arg, const struct netlink_compare_arg *x = arg->key; const struct netlink_sock *nlk = ptr; - return nlk->portid != x->portid || + return nlk->rhash_portid != x->portid || !net_eq(sock_net(&nlk->sk), read_pnet(&x->pnet)); } @@ -1043,7 +1043,7 @@ static int __netlink_insert(struct netlink_table *table, struct sock *sk) { struct netlink_compare_arg arg; - netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->portid); + netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->rhash_portid); return rhashtable_lookup_insert_key(&table->hash, &arg, &nlk_sk(sk)->node, netlink_rhashtable_params); @@ -1105,7 +1105,7 @@ static int netlink_insert(struct sock *sk, u32 portid) unlikely(atomic_read(&table->hash.nelems) >= UINT_MAX)) goto err; - nlk_sk(sk)->portid = portid; + nlk_sk(sk)->rhash_portid = portid; sock_hold(sk); err = __netlink_insert(table, sk); @@ -1117,10 +1117,11 @@ static int netlink_insert(struct sock *sk, u32 portid) err = -EOVERFLOW; if (err == -EEXIST) err = -EADDRINUSE; - nlk_sk(sk)->portid = 0; sock_put(sk); } + nlk_sk(sk)->portid = portid; + err: release_sock(sk); return err; @@ -3167,7 +3168,7 @@ static inline u32 netlink_hash(const void *data, u32 len, u32 seed) const struct netlink_sock *nlk = data; struct netlink_compare_arg arg; - netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->portid); + netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->rhash_portid); return jhash2((u32 *)&arg, netlink_compare_arg_len / sizeof(u32), seed); } diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h index df9a06090db6..80b2b7526dfd 100644 --- a/net/netlink/af_netlink.h +++ b/net/netlink/af_netlink.h @@ -25,6 +25,7 @@ struct netlink_ring { struct netlink_sock { /* struct sock has to be the first member of netlink_sock */ struct sock sk; + u32 rhash_portid; u32 portid; u32 dst_portid; u32 dst_group; -- cgit v1.2.3