netdev - [PATCH] ipv6 addrconf: enable use of proc_dointvec_minmax in addrconf

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Message-Id: <1474978605-28116-1-git-send-email-zenczykowski@gmail.com>
Date:   Tue, 27 Sep 2016 05:16:45 -0700
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Maciej Żenczykowski <maze@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Erik Kline <ek@...gle.com>,
        Lorenzo Colitti <lorenzo@...gle.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: [PATCH] ipv6 addrconf: enable use of proc_dointvec_minmax in addrconf_sysctl

From: Maciej Żenczykowski <maze@...gle.com>

Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
---
 net/ipv6/addrconf.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 2f1f5d439788..11fa1a5564d4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -6044,8 +6044,14 @@ static int __addrconf_sysctl_register(struct net *net, char *dev_name,
 
 	for (i = 0; table[i].data; i++) {
 		table[i].data += (char *)p - (char *)&ipv6_devconf;
-		table[i].extra1 = idev; /* embedded; no ref */
-		table[i].extra2 = net;
+		/* If one of these is already set, then it is not safe to
+		 * overwrite either of them: this makes proc_dointvec_minmax
+		 * usable.
+		 */
+		if (!table[i].extra1 && !table[i].extra2) {
+			table[i].extra1 = idev; /* embedded; no ref */
+			table[i].extra2 = net;
+		}
 	}
 
 	snprintf(path, sizeof(path), "net/ipv6/conf/%s", dev_name);
-- 
2.8.0.rc3.226.g39d4020