From: Wei Wang Date: Sat, 17 Jun 2017 17:42:31 +0000 (-0700) Subject: ipv4: call dst_hold_safe() properly X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=9df16efadd2a8a82731dc76ff656c771e261827f;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git 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 Acked-by: Martin KaFai Lau Signed-off-by: David S. Miller --- diff --git a/include/net/route.h b/include/net/route.h index 08e689f23365..cb0a76d9dde1 100644 --- a/include/net/route.h +++ b/include/net/route.h @@ -190,7 +190,9 @@ static inline int ip_route_input(struct sk_buff *skb, __be32 dst, __be32 src, rcu_read_lock(); err = ip_route_input_noref(skb, dst, src, tos, devin); if (!err) - skb_dst_force(skb); + skb_dst_force_safe(skb); + if (!skb_dst(skb)) + err = -EINVAL; rcu_read_unlock(); return err; 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: