userns: Use kgids for sysctl_ping_group_range

- Store sysctl_ping_group_range as a paire of kgid_t values
  instead of a pair of gid_t values.
- Move the kgid conversion work from ping_init_sock into ipv4_ping_group_range
- For invalid cases reset to the default disabled state.

With the kgid_t conversion made part of the original value sanitation
from userspace understand how the code will react becomes clearer
and it becomes possible to set the sysctl ping group range from
something other than the initial user namespace.

Cc: Vasiliy Kulikov <segoon@openwall.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 27 insertions, 15 deletions

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 1b5ce96707a..3e78c79b558 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -76,9 +76,9 @@ static int ipv4_local_port_range(ctl_table *table, int write,
 }
 
 
-static void inet_get_ping_group_range_table(struct ctl_table *table, gid_t *low, gid_t *high)
+static void inet_get_ping_group_range_table(struct ctl_table *table, kgid_t *low, kgid_t *high)
 {
-	gid_t *data = table->data;
+	kgid_t *data = table->data;
 	unsigned int seq;
 	do {
 		seq = read_seqbegin(&sysctl_local_ports.lock);
@@ -89,12 +89,12 @@ static void inet_get_ping_group_range_table(struct ctl_table *table, gid_t *low,
 }
 
 /* Update system visible IP port range */
-static void set_ping_group_range(struct ctl_table *table, gid_t range[2])
+static void set_ping_group_range(struct ctl_table *table, kgid_t low, kgid_t high)
 {
-	gid_t *data = table->data;
+	kgid_t *data = table->data;
 	write_seqlock(&sysctl_local_ports.lock);
-	data[0] = range[0];
-	data[1] = range[1];
+	data[0] = low;
+	data[1] = high;
 	write_sequnlock(&sysctl_local_ports.lock);
 }
 
@@ -103,21 +103,33 @@ static int ipv4_ping_group_range(ctl_table *table, int write,
 				 void __user *buffer,
 				 size_t *lenp, loff_t *ppos)
 {
+	struct user_namespace *user_ns = current_user_ns();
 	int ret;
-	gid_t range[2];
+	gid_t urange[2];
+	kgid_t low, high;
 	ctl_table tmp = {
-		.data = &range,
-		.maxlen = sizeof(range),
+		.data = &urange,
+		.maxlen = sizeof(urange),
 		.mode = table->mode,
 		.extra1 = &ip_ping_group_range_min,
 		.extra2 = &ip_ping_group_range_max,
 	};
 
-	inet_get_ping_group_range_table(table, range, range + 1);
+	inet_get_ping_group_range_table(table, &low, &high);
+	urange[0] = from_kgid_munged(user_ns, low);
+	urange[1] = from_kgid_munged(user_ns, high);
 	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 
-	if (write && ret == 0)
-		set_ping_group_range(table, range);
+	if (write && ret == 0) {
+		low = make_kgid(user_ns, urange[0]);
+		high = make_kgid(user_ns, urange[1]);
+		if (!gid_valid(low) || !gid_valid(high) ||
+		    (urange[1] < urange[0]) || gid_lt(high, low)) {
+			low = make_kgid(&init_user_ns, 1);
+			high = make_kgid(&init_user_ns, 0);
+		}
+		set_ping_group_range(table, low, high);
+	}
 
 	return ret;
 }
@@ -786,7 +798,7 @@ static struct ctl_table ipv4_net_table[] = {
 	{
 		.procname	= "ping_group_range",
 		.data		= &init_net.ipv4.sysctl_ping_group_range,
-		.maxlen		= sizeof(init_net.ipv4.sysctl_ping_group_range),
+		.maxlen		= sizeof(gid_t)*2,
 		.mode		= 0644,
 		.proc_handler	= ipv4_ping_group_range,
 	},
@@ -830,8 +842,8 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)
 	 * Sane defaults - nobody may create ping sockets.
 	 * Boot scripts should set this to distro-specific group.
 	 */
-	net->ipv4.sysctl_ping_group_range[0] = 1;
-	net->ipv4.sysctl_ping_group_range[1] = 0;
+	net->ipv4.sysctl_ping_group_range[0] = make_kgid(&init_user_ns, 1);
+	net->ipv4.sysctl_ping_group_range[1] = make_kgid(&init_user_ns, 0);
 
 	tcp_init_mem(net);