From: Eric Dumazet <edumazet@google.com>
Date: Wed, 31 May 2023 23:09:02 +0200

On Wed, May 31, 2023 at 9:19 PM Kuniyuki Iwashima [off-list ref] wrote:

quoted

From: ~akihirosuda <redacted>
Date: Wed, 31 May 2023 19:42:49 +0900

quoted

From: Akihiro Suda <redacted>

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.

In the implementation, proc_dointvec_minmax is no longer used because it
does not support numbers from 2147483648 to 4294967294.

Good catch.

I think we can use proc_doulongvec_minmax() instead of open coding.

With the diff below:

---8<---
# sysctl -a | grep ping
net.ipv4.ping_group_range = 0   2147483647
# sysctl -w net.ipv4.ping_group_range="0 4294967295"
sysctl: setting key "net.ipv4.ping_group_range": Invalid argument
# sysctl -w net.ipv4.ping_group_range="0 4294967294"
net.ipv4.ping_group_range = 0 4294967294
# sysctl -a | grep ping
net.ipv4.ping_group_range = 0   4294967294
---8<---

---8<---

diff --git a/include/net/ping.h b/include/net/ping.h
index 9233ad3de0ad..9b401b9a9d35 100644
--- a/include/net/ping.h
+++ b/include/net/ping.h

@@ -20,7 +20,7 @@
  * 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)

 /* Compatibility glue so we can support IPv6 when it's compiled as a module */
 struct pingv6_ops {

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 6ae3345a3bdf..11d401958673 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c

@@ -35,8 +35,8 @@ static int ip_ttl_max = 255;
 static int tcp_syn_retries_min = 1;
 static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
 static int tcp_syn_linear_timeouts_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 =

@@ -165,8 +165,8 @@ static int ipv4_ping_group_range(struct ctl_table *table, int write,
                                 void *buffer, size_t *lenp, loff_t *ppos)
 {
        struct user_namespace *user_ns = current_user_ns();
+       unsigned long urange[2];
        int ret;
-       gid_t urange[2];
        kgid_t low, high;
        struct ctl_table tmp = {
                .data = &urange,

@@ -179,7 +179,7 @@ static int ipv4_ping_group_range(struct ctl_table *table, int write,
        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]);
---8<---

Will this work on 32bit build ?

It worked at least on my i686 build and qemu.

---8<---
# uname -a
Linux (none) 6.4.0-rc3-00648-g75455b906d82-dirty #76 SMP PREEMPT_DYNAMIC Wed May 31 21:30:31 UTC 2023 i686 GNU/Linux
# sysctl -a | grep ping
net.ipv4.ping_group_range = 1	0
# sysctl -w net.ipv4.ping_group_range="0 4294967295"
sysctl: setting key "net.ipv4.ping_group_range": Invalid argument
# sysctl -w net.ipv4.ping_group_range="0 4294967294"
net.ipv4.ping_group_range = 0 4294967294
# sysctl -a | grep ping
net.ipv4.ping_group_range = 0	4294967294
---8<---