From 4dc6dc7162c08b9965163c9ab3f9375d4adff2c7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 15 Jul 2009 23:13:10 +0000 Subject: net: sock_copy() fixes Commit e912b1142be8f1e2c71c71001dc992c6e5eb2ec1 (net: sk_prot_alloc() should not blindly overwrite memory) took care of not zeroing whole new socket at allocation time. sock_copy() is another spot where we should be very careful. We should not set refcnt to a non null value, until we are sure other fields are correctly setup, or a lockless reader could catch this socket by mistake, while not fully (re)initialized. This patch puts sk_node & sk_refcnt to the very beginning of struct sock to ease sock_copy() & sk_prot_alloc() job. We add appropriate smp_wmb() before sk_refcnt initializations to match our RCU requirements (changes to sock keys should be committed to memory before sk_refcnt setting) Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/sock.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'net') diff --git a/net/core/sock.c b/net/core/sock.c index ba5d2116aea1..d9eec153d531 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -919,13 +919,19 @@ static inline void sock_lock_init(struct sock *sk) af_family_keys + sk->sk_family); } +/* + * Copy all fields from osk to nsk but nsk->sk_refcnt must not change yet, + * even temporarly, because of RCU lookups. sk_node should also be left as is. + */ static void sock_copy(struct sock *nsk, const struct sock *osk) { #ifdef CONFIG_SECURITY_NETWORK void *sptr = nsk->sk_security; #endif - - memcpy(nsk, osk, osk->sk_prot->obj_size); + BUILD_BUG_ON(offsetof(struct sock, sk_copy_start) != + sizeof(osk->sk_node) + sizeof(osk->sk_refcnt)); + memcpy(&nsk->sk_copy_start, &osk->sk_copy_start, + osk->sk_prot->obj_size - offsetof(struct sock, sk_copy_start)); #ifdef CONFIG_SECURITY_NETWORK nsk->sk_security = sptr; security_sk_clone(osk, nsk); @@ -1140,6 +1146,11 @@ struct sock *sk_clone(const struct sock *sk, const gfp_t priority) newsk->sk_err = 0; newsk->sk_priority = 0; + /* + * Before updating sk_refcnt, we must commit prior changes to memory + * (Documentation/RCU/rculist_nulls.txt for details) + */ + smp_wmb(); atomic_set(&newsk->sk_refcnt, 2); /* @@ -1855,6 +1866,11 @@ void sock_init_data(struct socket *sock, struct sock *sk) sk->sk_stamp = ktime_set(-1L, 0); + /* + * Before updating sk_refcnt, we must commit prior changes to memory + * (Documentation/RCU/rculist_nulls.txt for details) + */ + smp_wmb(); atomic_set(&sk->sk_refcnt, 1); atomic_set(&sk->sk_wmem_alloc, 1); atomic_set(&sk->sk_drops, 0); -- cgit v1.2.3-58-ga151