// 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 &current->nsproxy->net_ns->sysctls;
}

static int is_seen(struct ctl_table_set *set)
{
        return &current->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++, 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)
{
        if (!net_eq(net, &init_net))
                ensure_safe_net_sysctl(net, path, table, table_size);

        return __register_sysctl_table(&net->sysctls, path, table, table_size);
}
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);