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author | Eric Dumazet <edumazet@google.com> | 2014-06-24 21:05:11 +0400 |
---|---|---|
committer | Jiri Slaby <jslaby@suse.cz> | 2014-07-29 18:56:59 +0400 |
commit | 591b1e1bb40152e22cee757f493046a0ca946bf8 (patch) | |
tree | 70318ea1097beeb049d088598e39323eac55212d | |
parent | 1ea464333aa10210b8b285a8a64ce17211569156 (diff) | |
download | linux-591b1e1bb40152e22cee757f493046a0ca946bf8.tar.xz |
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: Jiri Slaby <jslaby@suse.cz>
-rw-r--r-- | include/net/sock.h | 4 | ||||
-rw-r--r-- | net/core/dst.c | 16 |
2 files changed, 13 insertions, 7 deletions
diff --git a/include/net/sock.h b/include/net/sock.h index 4aa873a6267f..dc84ec518ff5 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1749,8 +1749,8 @@ 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; } diff --git a/net/core/dst.c b/net/core/dst.c index ca4231ec7347..15b6792e6ebb 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -267,6 +267,15 @@ again: } EXPORT_SYMBOL(dst_destroy); +static void dst_destroy_rcu(struct rcu_head *head) +{ + struct dst_entry *dst = container_of(head, struct dst_entry, rcu_head); + + dst = dst_destroy(dst); + if (dst) + __dst_free(dst); +} + void dst_release(struct dst_entry *dst) { if (dst) { @@ -274,11 +283,8 @@ void dst_release(struct dst_entry *dst) newrefcnt = atomic_dec_return(&dst->__refcnt); WARN_ON(newrefcnt < 0); - if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) { - dst = dst_destroy(dst); - if (dst) - __dst_free(dst); - } + if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) + call_rcu(&dst->rcu_head, dst_destroy_rcu); } } EXPORT_SYMBOL(dst_release); |