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| author | Eric Dumazet <edumazet@google.com> | 2014-06-24 10:05:11 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-28 08:00:04 -0700 |
| commit | 86e48c03d774e01ccd71ecba4fc4b5c2bc0b5b41 (patch) | |
| tree | 65a2d12414c21cbeb61e636e5360399a0c63b18d /include | |
| parent | 1b56220b0df8f0963bacbf35637545b550484a64 (diff) | |
| download | lwn-86e48c03d774e01ccd71ecba4fc4b5c2bc0b5b41.tar.gz lwn-86e48c03d774e01ccd71ecba4fc4b5c2bc0b5b41.zip | |
ipv4: fix dst race in sk_dst_get()
[ Upstream commit f88649721268999bdff09777847080a52004f691 ]
When IP route cache had been removed in linux-3.6, we broke assumption
that dst entries were all freed after rcu grace period. DST_NOCACHE
dst were supposed to be freed from dst_release(). But it appears
we want to keep such dst around, either in UDP sockets or tunnels.
In sk_dst_get() we need to make sure dst refcount is not 0
before incrementing it, or else we might end up freeing a dst
twice.
DST_NOCACHE set on a dst does not mean this dst can not be attached
to a socket or a tunnel.
Then, before actual freeing, we need to observe a rcu grace period
to make sure all other cpus can catch the fact the dst is no longer
usable.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dormando <dormando@rydia.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/sock.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/net/sock.h b/include/net/sock.h index 72f710d2f75a..ff57aff205cd 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1727,8 +1727,8 @@ sk_dst_get(struct sock *sk) rcu_read_lock(); dst = rcu_dereference(sk->sk_dst_cache); - if (dst) - dst_hold(dst); + if (dst && !atomic_inc_not_zero(&dst->__refcnt)) + dst = NULL; rcu_read_unlock(); return dst; } |