From 8292d7f6e8712381a828eac2a19a610ce680c4dd Mon Sep 17 00:00:00 2001 From: Yang Yang Date: Mon, 19 Jul 2021 18:43:28 -0700 Subject: [PATCH] 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 Signed-off-by: Yang Yang Signed-off-by: David S. Miller --- net/ipv4/devinet.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c index d38124bd1b94..94b648d9eaff 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 */