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// SPDX-License-Identifier: GPL-2.0-only
/* -*- linux-c -*-
* sysctl_net.c: sysctl interface to net subsystem.
*
* Begun April 1, 1996, Mike Shaver.
* Added /proc/sys/net directories for each protocol family. [MS]
*
* Revision 1.2 1996/05/08 20:24:40 shaver
* Added bits for NET_BRIDGE and the NET_IPV4_ARP stuff and
* NET_IPV4_IP_FORWARD.
*
*
*/
#include <linux/mm.h>
#include <linux/export.h>
#include <linux/sysctl.h>
#include <linux/nsproxy.h>
#include <net/sock.h>
#ifdef CONFIG_INET
#include <net/ip.h>
#endif
#ifdef CONFIG_NET
#include <linux/if_ether.h>
#endif
static struct ctl_table_set *
net_ctl_header_lookup(struct ctl_table_root *root)
{
return ¤t->nsproxy->net_ns->sysctls;
}
static int is_seen(struct ctl_table_set *set)
{
return ¤t->nsproxy->net_ns->sysctls == set;
}
/* Return standard mode bits for table entry. */
static int net_ctl_permissions(struct ctl_table_header *head,
const struct ctl_table *table)
{
struct net *net = container_of(head->set, struct net, sysctls);
/* Allow network administrator to have same access as root. */
if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN)) {
int mode = (table->mode >> 6) & 7;
return (mode << 6) | (mode << 3) | mode;
}
return table->mode;
}
static void net_ctl_set_ownership(struct ctl_table_header *head,
kuid_t *uid, kgid_t *gid)
{
struct net *net = container_of(head->set, struct net, sysctls);
kuid_t ns_root_uid;
kgid_t ns_root_gid;
ns_root_uid = make_kuid(net->user_ns, 0);
if (uid_valid(ns_root_uid))
*uid = ns_root_uid;
ns_root_gid = make_kgid(net->user_ns, 0);
if (gid_valid(ns_root_gid))
*gid = ns_root_gid;
}
static struct ctl_table_root net_sysctl_root = {
.lookup = net_ctl_header_lookup,
.permissions = net_ctl_permissions,
.set_ownership = net_ctl_set_ownership,
};
static int __net_init sysctl_net_init(struct net *net)
{
setup_sysctl_set(&net->sysctls, &net_sysctl_root, is_seen);
return 0;
}
static void __net_exit sysctl_net_exit(struct net *net)
{
retire_sysctl_set(&net->sysctls);
}
static struct pernet_operations sysctl_pernet_ops = {
.init = sysctl_net_init,
.exit = sysctl_net_exit,
};
static struct ctl_table_header *net_header;
__init int net_sysctl_init(void)
{
static struct ctl_table empty[1];
int ret = -ENOMEM;
/* Avoid limitations in the sysctl implementation by
* registering "/proc/sys/net" as an empty directory not in a
* network namespace.
*/
net_header = register_sysctl_sz("net", empty, 0);
if (!net_header)
goto out;
ret = register_pernet_subsys(&sysctl_pernet_ops);
if (ret)
goto out1;
out:
return ret;
out1:
unregister_sysctl_table(net_header);
net_header = NULL;
goto out;
}
/* Verify that sysctls for non-init netns are safe by either:
* 1) being read-only, or
* 2) having a data pointer which points outside of the global kernel/module
* data segment, and rather into the heap where a per-net object was
* allocated.
*/
static void ensure_safe_net_sysctl(struct net *net, const char *path,
struct ctl_table *table, size_t table_size)
{
struct ctl_table *ent;
pr_debug("Registering net sysctl (net %p): %s\n", net, path);
ent = table;
for (size_t i = 0; i < table_size && ent->procname; ent++, i++) {
unsigned long addr;
const char *where;
pr_debug(" procname=%s mode=%o proc_handler=%ps data=%p\n",
ent->procname, ent->mode, ent->proc_handler, ent->data);
/* If it's not writable inside the netns, then it can't hurt. */
if ((ent->mode & 0222) == 0) {
pr_debug(" Not writable by anyone\n");
continue;
}
/* Where does data point? */
addr = (unsigned long)ent->data;
if (is_module_address(addr))
where = "module";
else if (is_kernel_core_data(addr))
where = "kernel";
else
continue;
/* If it is writable and points to kernel/module global
* data, then it's probably a netns leak.
*/
WARN(1, "sysctl %s/%s: data points to %s global data: %ps\n",
path, ent->procname, where, ent->data);
/* Make it "safe" by dropping writable perms */
ent->mode &= ~0222;
}
}
struct ctl_table_header *register_net_sysctl_sz(struct net *net,
const char *path,
struct ctl_table *table,
size_t table_size)
{
int count;
struct ctl_table *entry;
if (!net_eq(net, &init_net))
ensure_safe_net_sysctl(net, path, table, table_size);
entry = table;
for (count = 0 ; count < table_size && entry->procname; entry++, count++)
;
return __register_sysctl_table(&net->sysctls, path, table, count);
}
EXPORT_SYMBOL_GPL(register_net_sysctl_sz);
void unregister_net_sysctl_table(struct ctl_table_header *header)
{
unregister_sysctl_table(header);
}
EXPORT_SYMBOL_GPL(unregister_net_sysctl_table);
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