diff options
| author | Eric Dumazet <edumazet@google.com> | 2014-06-24 21:05:11 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-06-26 04:41:44 +0400 |
| commit | f88649721268999bdff09777847080a52004f691 (patch) | |
| tree | 909bff5bf235780ccec651d41bfc8a370ba7ff27 /include/net | |
| parent | 99e72a0fed07d118d329f3046ad2ec2ae9357d63 (diff) | |
| download | linux-f88649721268999bdff09777847080a52004f691.tar.xz | |
ipv4: fix dst race in sk_dst_get()
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>
Diffstat (limited to 'include/net')
| -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 07b7fcd60d80..173cae485de1 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1730,8 +1730,8 @@ 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; } |