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authorWei Wang <weiwan@google.com>2017-06-17 10:42:31 -0700
committerDavid S. Miller <davem@davemloft.net>2017-06-17 22:54:00 -0400
commit9df16efadd2a8a82731dc76ff656c771e261827f (patch)
treee43af92481dcf7517e8c7e086cfccecbc6bd0792 /net/ipv4
parent95c47f9cf5e028d1ae77dc6c767c1edc8a18025b (diff)
ipv4: call dst_hold_safe() properly
This patch checks all the calls to dst_hold()/skb_dst_force()/dst_clone()/dst_use() to see if dst_hold_safe() is needed to avoid double free issue if dst gc is removed and dst_release() directly destroys dst when dst->__refcnt drops to 0. In tx path, TCP hold sk->sk_rx_dst ref count and also hold sock_lock(). UDP and other similar protocols always hold refcount for skb->_skb_refdst. So both paths seem to be safe. In rx path, as it is lockless and skb_dst_set_noref() is likely to be used, dst_hold_safe() should always be used when trying to hold dst. In the routing code, if dst is held during an rcu protected session, it is necessary to call dst_hold_safe() as the current dst might be in its rcu grace period. Signed-off-by: Wei Wang <weiwan@google.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/route.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index d986d80258d2..903a12c601ac 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2234,10 +2234,8 @@ static struct rtable *__mkroute_output(const struct fib_result *res,
rth = rcu_dereference(*prth);
rt_cache:
- if (rt_cache_valid(rth)) {
- dst_hold(&rth->dst);
+ if (rt_cache_valid(rth) && dst_hold_safe(&rth->dst))
return rth;
- }
}
add: