linux-kernel - [PATCH 4.18 20/88] net/ipv6: do not copy dst flags on rt init

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Date:   Thu, 27 Sep 2018 11:03:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Ahern <dsahern@...il.com>,
        Wei Wang <weiwan@...gle.com>, Peter Oskolkov <posk@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.18 20/88] net/ipv6: do not copy dst flags on rt init

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Oskolkov <posk@...gle.com>

[ Upstream commit 30bfd93062814d6767e452a8f5ddcd97f7e38c7e ]

DST_NOCOUNT in dst_entry::flags tracks whether the entry counts
toward route cache size (net->ipv6.sysctl.ip6_rt_max_size).

If the flag is NOT set, dst_ops::pcpuc_entries counter is incremented
in dist_init() and decremented in dst_destroy().

This flag is tied to allocation/deallocation of dst_entry and
should not be copied from another dst/route. Otherwise it can happen
that dst_ops::pcpuc_entries counter grows until no new routes can
be allocated because the counter reached ip6_rt_max_size due to
DST_NOCOUNT not set and thus no counter decrements on gc-ed routes.

Fixes: 3b6761d18bc1 ("net/ipv6: Move dst flags to booleans in fib entries")
Cc: David Ahern <dsahern@...il.com>
Acked-by: Wei Wang <weiwan@...gle.com>
Signed-off-by: Peter Oskolkov <posk@...gle.com>
Reviewed-by: David Ahern <dsahern@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/route.c |    2 --
 1 file changed, 2 deletions(-)

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -946,8 +946,6 @@ static void ip6_rt_init_dst_reject(struc

 static void ip6_rt_init_dst(struct rt6_info *rt, struct fib6_info *ort)
 {
-	rt->dst.flags |= fib6_info_dst_flags(ort);
-
 	if (ort->fib6_flags & RTF_REJECT) {
 		ip6_rt_init_dst_reject(rt, ort);
 		return;