netdev - [PATCH net 2/2] ipv6: fix memory leak on dst->

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Message-Id: <20180918204500.106240-3-tracywwnj@gmail.com>
Date:   Tue, 18 Sep 2018 13:45:00 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Sabrina Dubroca <sd@...asysnail.net>,
        Wei Wang <weiwan@...gle.com>
Subject: [PATCH net 2/2] ipv6: fix memory leak on dst->_metrics

From: Wei Wang <weiwan@...gle.com>

When dst->_metrics and f6i->fib6_metrics share the same memory, both
take reference count on the dst_metrics structure. However, when dst is
destroyed, ip6_dst_destroy() only invokes dst_destroy_metrics_generic()
which does not take care of READONLY metrics and does not release refcnt.
This causes memory leak.
Similar to ipv4 logic, the fix is to properly release refcnt and free
the memory space pointed by dst->_metrics if refcnt becomes 0.

Fixes: 93531c674315 ("net/ipv6: separate handling of FIB entries from dst based routes")
Reported-by: Sabrina Dubroca <sd@...asysnail.net>
Signed-off-by: Wei Wang <weiwan@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/route.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index b5d3e6b294ab..826b14de7dbb 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -364,11 +364,14 @@ EXPORT_SYMBOL(ip6_dst_alloc);
 
 static void ip6_dst_destroy(struct dst_entry *dst)
 {
+	struct dst_metrics *p = (struct dst_metrics *)DST_METRICS_PTR(dst);
 	struct rt6_info *rt = (struct rt6_info *)dst;
 	struct fib6_info *from;
 	struct inet6_dev *idev;
 
-	dst_destroy_metrics_generic(dst);
+	if (p != &dst_default_metrics && refcount_dec_and_test(&p->refcnt))
+		kfree(p);
+
 	rt6_uncached_list_del(rt);
 
 	idev = rt->rt6i_idev;
-- 
2.19.0.397.gdd90340f6a-goog