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authorEric Dumazet <eric.dumazet@gmail.com>2009-07-15 23:13:10 +0000
committerDavid S. Miller <davem@davemloft.net>2009-07-16 18:05:26 -0700
commit4dc6dc7162c08b9965163c9ab3f9375d4adff2c7 (patch)
treef4b9959e9ca5e5b8bdb6301663a15e0f67d4c68c /net/core/sock.c
parent303d67c288319768b19ed8dbed429fef7eb7c275 (diff)
downloadlinux-4dc6dc7162c08b9965163c9ab3f9375d4adff2c7.tar.bz2
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 <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/sock.c')
-rw-r--r--net/core/sock.c20
1 files changed, 18 insertions, 2 deletions
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);