// 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,

  			       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,
  				  struct ctl_table *table,
  				  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("net", empty);
  	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)
  {
  	struct ctl_table *ent;
  
  	pr_debug("Registering net sysctl (net %p): %s
  ", net, path);
  	for (ent = table; ent->procname; ent++) {
  		unsigned long addr;
  		const char *where;
  
  		pr_debug("  procname=%s mode=%o proc_handler=%ps data=%p
  ",
  			 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
  ");
  			continue;
  		}
  
  		/* Where does data point? */
  		addr = (unsigned long)ent->data;
  		if (is_module_address(addr))
  			where = "module";
  		else if (core_kernel_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
  ",
  		     path, ent->procname, where, ent->data);
  
  		/* Make it "safe" by dropping writable perms */
  		ent->mode &= ~0222;
  	}
  }

  struct ctl_table_header *register_net_sysctl(struct net *net,
  	const char *path, struct ctl_table *table)
  {

  	if (!net_eq(net, &init_net))
  		ensure_safe_net_sysctl(net, path, table);

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

  void unregister_net_sysctl_table(struct ctl_table_header *header)
  {

  	unregister_sysctl_table(header);

  }
  EXPORT_SYMBOL_GPL(unregister_net_sysctl_table);