1// SPDX-License-Identifier: GPL-2.0
2#include <linux/cred.h>
3#include <linux/init.h>
4#include <linux/kernel.h>
5#include <linux/quotaops.h>
6#include <linux/sched.h>
7#include <linux/slab.h>
8#include <net/netlink.h>
9#include <net/genetlink.h>
10
11static const struct genl_multicast_group quota_mcgrps[] = {
12	{ .name = "events", },
13};
14
15/* Netlink family structure for quota */
16static struct genl_family quota_genl_family __ro_after_init = {
17	.module = THIS_MODULE,
18	.hdrsize = 0,
19	.name = "VFS_DQUOT",
20	.version = 1,
21	.maxattr = QUOTA_NL_A_MAX,
22	.mcgrps = quota_mcgrps,
23	.n_mcgrps = ARRAY_SIZE(quota_mcgrps),
24};
25
26/**
27 * quota_send_warning - Send warning to userspace about exceeded quota
28 * @qid: The kernel internal quota identifier.
29 * @dev: The device on which the fs is mounted (sb->s_dev)
30 * @warntype: The type of the warning: QUOTA_NL_...
31 *
32 * This can be used by filesystems (including those which don't use
33 * dquot) to send a message to userspace relating to quota limits.
34 *
35 */
36
37void quota_send_warning(struct kqid qid, dev_t dev,
38			const char warntype)
39{
40	static atomic_t seq;
41	struct sk_buff *skb;
42	void *msg_head;
43	int ret;
44	int msg_size = 4 * nla_total_size(sizeof(u32)) +
45		       2 * nla_total_size_64bit(sizeof(u64));
46
47	/* We have to allocate using GFP_NOFS as we are called from a
48	 * filesystem performing write and thus further recursion into
49	 * the fs to free some data could cause deadlocks. */
50	skb = genlmsg_new(msg_size, GFP_NOFS);
51	if (!skb) {
52		printk(KERN_ERR
53		  "VFS: Not enough memory to send quota warning.\n");
54		return;
55	}
56	msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
57			&quota_genl_family, 0, QUOTA_NL_C_WARNING);
58	if (!msg_head) {
59		printk(KERN_ERR
60		  "VFS: Cannot store netlink header in quota warning.\n");
61		goto err_out;
62	}
63	ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
64	if (ret)
65		goto attr_err_out;
66	ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
67				from_kqid_munged(&init_user_ns, qid),
68				QUOTA_NL_A_PAD);
69	if (ret)
70		goto attr_err_out;
71	ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
72	if (ret)
73		goto attr_err_out;
74	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
75	if (ret)
76		goto attr_err_out;
77	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
78	if (ret)
79		goto attr_err_out;
80	ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
81				from_kuid_munged(&init_user_ns, current_uid()),
82				QUOTA_NL_A_PAD);
83	if (ret)
84		goto attr_err_out;
85	genlmsg_end(skb, msg_head);
86
87	genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);
88	return;
89attr_err_out:
90	printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
91err_out:
92	kfree_skb(skb);
93}
94EXPORT_SYMBOL(quota_send_warning);
95
96static int __init quota_init(void)
97{
98	if (genl_register_family(&quota_genl_family) != 0)
99		printk(KERN_ERR
100		       "VFS: Failed to create quota netlink interface.\n");
101	return 0;
102};
103fs_initcall(quota_init);
104