path: root/net/netlink/genetlink.c

// SPDX-License-Identifier: GPL-2.0
/*
 * NETLINK      Generic Netlink Family
 *
 * 		Authors:	Jamal Hadi Salim
 * 				Thomas Graf <tgraf@suug.ch>
 *				Johannes Berg <johannes@sipsolutions.net>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/mutex.h>
#include <linux/bitmap.h>
#include <linux/rwsem.h>
#include <linux/idr.h>
#include <net/sock.h>
#include <net/genetlink.h>

static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
static DECLARE_RWSEM(cb_lock);

atomic_t genl_sk_destructing_cnt = ATOMIC_INIT(0);
DECLARE_WAIT_QUEUE_HEAD(genl_sk_destructing_waitq);

void genl_lock(void)
{
	mutex_lock(&genl_mutex);
}
EXPORT_SYMBOL(genl_lock);

void genl_unlock(void)
{
	mutex_unlock(&genl_mutex);
}
EXPORT_SYMBOL(genl_unlock);

static void genl_lock_all(void)
{
	down_write(&cb_lock);
	genl_lock();
}

static void genl_unlock_all(void)
{
	genl_unlock();
	up_write(&cb_lock);
}

static DEFINE_IDR(genl_fam_idr);

/*
 * Bitmap of multicast groups that are currently in use.
 *
 * To avoid an allocation at boot of just one unsigned long,
 * declare it global instead.
 * Bit 0 is marked as already used since group 0 is invalid.
 * Bit 1 is marked as already used since the drop-monitor code
 * abuses the API and thinks it can statically use group 1.
 * That group will typically conflict with other groups that
 * any proper users use.
 * Bit 16 is marked as used since it's used for generic netlink
 * and the code no longer marks pre-reserved IDs as used.
 * Bit 17 is marked as already used since the VFS quota code
 * also abused this API and relied on family == group ID, we
 * cater to that by giving it a static family and group ID.
 * Bit 18 is marked as already used since the PMCRAID driver
 * did the same thing as the VFS quota code (maybe copied?)
 */
static unsigned long mc_group_start = 0x3 | BIT(GENL_ID_CTRL) |
				      BIT(GENL_ID_VFS_DQUOT) |
				      BIT(GENL_ID_PMCRAID);
static unsigned long *mc_groups = &mc_group_start;
static unsigned long mc_groups_longs = 1;

/* We need the last attribute with non-zero ID therefore a 2-entry array */
static struct nla_policy genl_policy_reject_all[] = {
	{ .type = NLA_REJECT },
	{ .type = NLA_REJECT },
};

static int genl_ctrl_event(int event, const struct genl_family *family,
			   const struct genl_multicast_group *grp,
			   int grp_id);

static void
genl_op_fill_in_reject_policy(const struct genl_family *family,
			      struct genl_ops *op)
{
	BUILD_BUG_ON(ARRAY_SIZE(genl_policy_reject_all) - 1 != 1);

	if (op->policy || op->cmd < family->resv_start_op)
		return;

	op->policy = genl_policy_reject_all;
	op->maxattr = 1;
}

static const struct genl_family *genl_family_find_byid(unsigned int id)
{
	return idr_find(&genl_fam_idr, id);
}

static const struct genl_family *genl_family_find_byname(char *name)
{
	const struct genl_family *family;
	unsigned int id;

	idr_for_each_entry(&genl_fam_idr, family, id)
		if (strcmp(family->name, name) == 0)
			return family;

	return NULL;
}

static int genl_get_cmd_cnt(const struct genl_family *family)
{
	return family->n_ops + family->n_small_ops;
}

static void genl_op_from_full(const struct genl_family *family,
			      unsigned int i, struct genl_ops *op)
{
	*op = family->ops[i];

	if (!op->maxattr)
		op->maxattr = family->maxattr;
	if (!op->policy)
		op->policy = family->policy;

	genl_op_fill_in_reject_policy(family, op);
}

static int genl_get_cmd_full(u32 cmd, const struct genl_family *family,
			     struct genl_ops *op)
{
	int i;

	for (i = 0; i < family->n_ops; i++)
		if (family->ops[i].cmd == cmd) {
			genl_op_from_full(family, i, op);
			return 0;
		}

	return -ENOENT;
}

static void genl_op_from_small(const struct genl_family *family,
			       unsigned int i, struct genl_ops *op)
{
	memset(op, 0, sizeof(*op));
	op->doit	= family->small_ops[i].doit;
	op->dumpit	= family->small_ops[i].dumpit;
	op->cmd		= family->small_ops[i].cmd;
	op->internal_flags = family->small_ops[i].internal_flags;
	op->flags	= family->small_ops[i].flags;
	op->validate	= family->small_ops[i].validate;

	op->maxattr = family->maxattr;
	op->policy = family->policy;

	genl_op_fill_in_reject_policy(family, op);
}

static int genl_get_cmd_small(u32 cmd, const struct genl_family *family,
			      struct genl_ops *op)
{
	int i;

	for (i = 0; i < family->n_small_ops; i++)
		if (family->small_ops[i].cmd == cmd) {
			genl_op_from_small(family, i, op);
			return 0;
		}

	return -ENOENT;
}

static int genl_get_cmd(u32 cmd, const struct genl_family *family,
			struct genl_ops *op)
{
	if (!genl_get_cmd_full(cmd, family, op))
		return 0;
	return genl_get_cmd_small(cmd, family, op);
}

static void genl_get_cmd_by_index(unsigned int i,
				  const struct genl_family *family,
				  struct genl_ops *op)
{
	if (i < family->n_ops)
		genl_op_from_full(family, i, op);
	else if (i < family->n_ops + family->n_small_ops)
		genl_op_from_small(family, i - family->n_ops, op);
	else
		WARN_ON_ONCE(1);
}

static int genl_allocate_reserve_groups(int n_groups, int *first_id)
{
	unsigned long *new_groups;
	int start = 0;
	int i;
	int id;
	bool fits;

	do {
		if (start == 0)
			id = find_first_zero_bit(mc_groups,
						 mc_groups_longs *
						 BITS_PER_LONG);
		else
			id = find_next_zero_bit(mc_groups,
						mc_groups_longs * BITS_PER_LONG,
						start);

		fits = true;
		for (i = id;
		     i < min_t(int, id + n_groups,
			       mc_groups_longs * BITS_PER_LONG);
		     i++) {
			if (test_bit(i, mc_groups)) {
				start = i;
				fits = false;
				break;
			}
		}

		if (id + n_groups > mc_groups_longs * BITS_PER_LONG) {
			unsigned long new_longs = mc_groups_longs +