net: ipv4: add capability check for net administration
Root in init user namespace can modify /proc/sys/net/ipv4/ip_forward
without CAP_NET_ADMIN, this doesn't follow the principle of
capabilities. For example, let's take a look at netdev_store(),
root can't modify netdev attribute without CAP_NET_ADMIN.
So let's keep the consistency of permission check logic.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index d38124b..94b648d 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2424,11 +2424,15 @@ static int devinet_sysctl_forward(struct ctl_table *ctl, int write,
int *valp = ctl->data;
int val = *valp;
loff_t pos = *ppos;
- int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
+ struct net *net = ctl->extra2;
+ int ret;
+
+ if (write && !ns_capable(net->user_ns, CAP_NET_ADMIN))
+ return -EPERM;
+
+ ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
if (write && *valp != val) {
- struct net *net = ctl->extra2;
-
if (valp != &IPV4_DEVCONF_DFLT(net, FORWARDING)) {
if (!rtnl_trylock()) {
/* Restore the original values before restarting */