diff options
author | Eric Dumazet <edumazet@google.com> | 2014-06-24 17:05:11 (GMT) |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-06-26 00:41:44 (GMT) |
commit | f88649721268999bdff09777847080a52004f691 (patch) | |
tree | 909bff5bf235780ccec651d41bfc8a370ba7ff27 /net/ipv4/ip_tunnel.c | |
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 'net/ipv4/ip_tunnel.c')
-rw-r--r-- | net/ipv4/ip_tunnel.c | 14 |
1 files changed, 5 insertions, 9 deletions
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c index 097b3e7..54b6731 100644 --- a/net/ipv4/ip_tunnel.c +++ b/net/ipv4/ip_tunnel.c @@ -73,12 +73,7 @@ static void __tunnel_dst_set(struct ip_tunnel_dst *idst, { struct dst_entry *old_dst; - if (dst) { - if (dst->flags & DST_NOCACHE) - dst = NULL; - else - dst_clone(dst); - } + dst_clone(dst); old_dst = xchg((__force struct dst_entry **)&idst->dst, dst); dst_release(old_dst); } @@ -108,13 +103,14 @@ static struct rtable *tunnel_rtable_get(struct ip_tunnel *t, u32 cookie) rcu_read_lock(); dst = rcu_dereference(this_cpu_ptr(t->dst_cache)->dst); + if (dst && !atomic_inc_not_zero(&dst->__refcnt)) + dst = NULL; if (dst) { if (dst->obsolete && dst->ops->check(dst, cookie) == NULL) { - rcu_read_unlock(); tunnel_dst_reset(t); - return NULL; + dst_release(dst); + dst = NULL; } - dst_hold(dst); } rcu_read_unlock(); return (struct rtable *)dst; |