addrconf: always initialize sysctl table data

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>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 17f8e7ea133b49801f49791c5f9c1968e8584e88..1f21087accab258e5be6cc104f8b8ced13fedd6d 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5369,13 +5369,10 @@ 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);