addrconf: always initialize sysctl table data

Orabug: 23330541

[ Upstream commit 5449a5ca9bc27dd51a462de7ca0b1cd861cd2bd0 ]

When sysctl performs restrict writes, it allows to write from
a middle position of a sysctl file, which requires us to initialize
the table data before calling proc_dostring() for the write case.

Fixes: 3d1bec99320d ("ipv6: introduce secret_stable to ipv6_devconf")
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 6866b52c56db189f8471a13f951221c45c0089c7)

Signed-off-by: Dan Duval <dan.duval@oracle.com>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 53d035347326b1f206989a2ee695d17fae40882d..69cb7687a30db2d3b6ae4b794a3e19cd1de4d05e 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5260,13 +5260,10 @@ static int addrconf_sysctl_stable_secret(struct ctl_table *ctl, int write,
                goto out;
        }
 
-       if (!write) {
-               err = snprintf(str, sizeof(str), "%pI6",
-                              &secret->secret);
-               if (err >= sizeof(str)) {
-                       err = -EIO;
-                       goto out;
-               }
+       err = snprintf(str, sizeof(str), "%pI6", &secret->secret);
+       if (err >= sizeof(str)) {
+               err = -EIO;
+               goto out;
        }
 
        err = proc_dostring(&lctl, write, buffer, lenp, ppos);