net/ipv4: ping_group_range: allow GID from 2147483648 to 4294967294

With this commit, all the GIDs ("0 4294967294") can be written to the
"net.ipv4.ping_group_range" sysctl.

Note that 4294967295 (0xffffffff) is an invalid GID (see gid_valid() in
include/linux/uidgid.h), and an attempt to register this number will cause
-EINVAL.

Prior to this commit, only up to GID 2147483647 could be covered.
Documentation/networking/ip-sysctl.rst had "0 4294967295" as an example
value, but this example was wrong and causing -EINVAL.

Fixes: c319b4d76b9e ("net: ipv4: add IPPROTO_ICMP socket kind")
Co-developed-by: Kuniyuki Iwashima <[e-mail]>
Signed-off-by: Kuniyuki Iwashima <[e-mail]>
Signed-off-by: Akihiro Suda <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/networking/ip-sysctl.rst

···
 	Restrict ICMP_PROTO datagram sockets to users in the group range.
 	The default is "1 0", meaning, that nobody (not even root) may
 	create ping sockets.  Setting it to "100 100" would grant permissions
-	to the single group. "0 4294967295" would enable it for the world, "100
-	4294967295" would enable it for the users, but not daemons.
+	to the single group. "0 4294967294" would enable it for the world, "100
+	4294967294" would enable it for the users, but not daemons.
 
 tcp_early_demux - BOOLEAN
 	Enable early demux for established TCP sockets.

include/net/ping.h

···
 #define PING_HTABLE_SIZE 	64
 #define PING_HTABLE_MASK 	(PING_HTABLE_SIZE-1)
 
-/*
- * gid_t is either uint or ushort.  We want to pass it to
- * proc_dointvec_minmax(), so it must not be larger than MAX_INT
- */
-#define GID_T_MAX (((gid_t)~0U) >> 1)
+#define GID_T_MAX (((gid_t)~0U) - 1)
 
 /* Compatibility glue so we can support IPv6 when it's compiled as a module */
 struct pingv6_ops {

net/ipv4/sysctl_net_ipv4.c

···
 static int ip_ttl_max = 255;
 static int tcp_syn_retries_min = 1;
 static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
-static int ip_ping_group_range_min[] = { 0, 0 };
-static int ip_ping_group_range_max[] = { GID_T_MAX, GID_T_MAX };
+static unsigned long ip_ping_group_range_min[] = { 0, 0 };
+static unsigned long ip_ping_group_range_max[] = { GID_T_MAX, GID_T_MAX };
 static u32 u32_max_div_HZ = UINT_MAX / HZ;
 static int one_day_secs = 24 * 3600;
 static u32 fib_multipath_hash_fields_all_mask __maybe_unused =
···
 {
 	struct user_namespace *user_ns = current_user_ns();
 	int ret;
-	gid_t urange[2];
+	unsigned long urange[2];
 	kgid_t low, high;
 	struct ctl_table tmp = {
 		.data = &urange,
···
 	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);
+	ret = proc_doulongvec_minmax(&tmp, write, buffer, lenp, ppos);
 
 	if (write && ret == 0) {
 		low = make_kgid(user_ns, urange[0]);