From 3cdaedae635b17ce23c738ce7d364b442310cdec Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 4 Dec 2009 03:47:42 +0000 Subject: tcp: Fix a connect() race with timewait sockets When we find a timewait connection in __inet_hash_connect() and reuse it for a new connection request, we have a race window, releasing bind list lock and reacquiring it in __inet_twsk_kill() to remove timewait socket from list. Another thread might find the timewait socket we already chose, leading to list corruption and crashes. Fix is to remove timewait socket from bind list before releasing the bind lock. Note: This problem happens if sysctl_tcp_tw_reuse is set. Reported-by: kapil dakhane Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/inet_hashtables.c | 2 ++ net/ipv4/inet_timewait_sock.c | 29 +++++++++++++++++++++-------- 2 files changed, 23 insertions(+), 8 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index c4201b7ece3..2b79377b468 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -502,6 +502,8 @@ ok: inet_sk(sk)->inet_sport = htons(port); twrefcnt += hash(sk, tw); } + if (tw) + twrefcnt += inet_twsk_bind_unhash(tw, hinfo); spin_unlock(&head->lock); if (tw) { diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index 0fdf45e4c90..bf4b1e2a430 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -29,12 +29,29 @@ int inet_twsk_unhash(struct inet_timewait_sock *tw) return 1; } +/* + * unhash a timewait socket from bind hash + * lock must be hold by caller + */ +int inet_twsk_bind_unhash(struct inet_timewait_sock *tw, + struct inet_hashinfo *hashinfo) +{ + struct inet_bind_bucket *tb = tw->tw_tb; + + if (!tb) + return 0; + + __hlist_del(&tw->tw_bind_node); + tw->tw_tb = NULL; + inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); + return 1; +} + /* Must be called with locally disabled BHs. */ static void __inet_twsk_kill(struct inet_timewait_sock *tw, struct inet_hashinfo *hashinfo) { struct inet_bind_hashbucket *bhead; - struct inet_bind_bucket *tb; int refcnt; /* Unlink from established hashes. */ spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash); @@ -46,15 +63,11 @@ static void __inet_twsk_kill(struct inet_timewait_sock *tw, /* Disassociate with bind bucket. */ bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num, hashinfo->bhash_size)]; + spin_lock(&bhead->lock); - tb = tw->tw_tb; - if (tb) { - __hlist_del(&tw->tw_bind_node); - tw->tw_tb = NULL; - inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb); - refcnt++; - } + refcnt += inet_twsk_bind_unhash(tw, hashinfo); spin_unlock(&bhead->lock); + #ifdef SOCK_REFCNT_DEBUG if (atomic_read(&tw->tw_refcnt) != 1) { printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n", -- cgit v1.2.3-70-g09d2