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net: Fix sock_wfree() race

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Commit 2b85a34e91
(net: No more expensive sock_hold()/sock_put() on each tx)
opens a window in sock_wfree() where another cpu
might free the socket we are working on.

A fix is to call sk->sk_write_space(sk) while still
holding a reference on sk.

Reported-by: Jike Song <albcamus@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2009-09-24 10:49:24 +00:00 • committed by David S. Miller
commit d99927f4d9
1 changed files with 12 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

21
net/core/sock.c
View file

@ -1228,17 +1228,22 @@ void __init sk_init(void)
void sock_wfree(struct sk_buff *skb)
{
struct sock *sk = skb->sk;
int res;
unsigned int len = skb->truesize;
/* In case it might be waiting for more memory. */
res = atomic_sub_return(skb->truesize, &sk->sk_wmem_alloc);
if (!sock_flag(sk, SOCK_USE_WRITE_QUEUE))
sk->sk_write_space(sk);
if (!sock_flag(sk, SOCK_USE_WRITE_QUEUE)) {
/*
* if sk_wmem_alloc reached 0, we are last user and should
* free this sock, as sk_free() call could not do it.
* Keep a reference on sk_wmem_alloc, this will be released
* after sk_write_space() call
*/
if (res == 0)
atomic_sub(len - 1, &sk->sk_wmem_alloc);
sk->sk_write_space(sk);
len = 1;
}
/*
* if sk_wmem_alloc reaches 0, we must finish what sk_free()
* could not do because of in-flight packets
*/
if (atomic_sub_and_test(len, &sk->sk_wmem_alloc))
__sk_free(sk);
}
EXPORT_SYMBOL(sock_wfree);