[PATCH] ipv6 addrconf: enable use of proc_dointvec_minmax in addrconf_sysctl

[Maciej Żenczykowski]

From: Maciej Żenczykowski <m...@google.com>

Signed-off-by: Maciej Żenczykowski <m...@google.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