diff options
| author | Eric Dumazet <edumazet@google.com> | 2014-06-24 10:05:11 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-07-28 08:08:23 -0700 |
| commit | 9a4fe697023dbe6c25caa1f8b2153af869a29bd2 (patch) | |
| tree | 016e8816153beb4fb78621bebaf8d2a6c5ecd645 /include | |
| parent | d5edc54bdcd1996389182a3a6654cf87b4ce23cb (diff) | |
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 21569cf456ed..bef0aabc95a7 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1728,8 +1728,8 @@ 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; } |