1
2#include <linux/cred.h>
3#include <linux/init.h>
4#include <linux/module.h>
5#include <linux/kernel.h>
6#include <linux/quotaops.h>
7#include <linux/sched.h>
8#include <linux/slab.h>
9#include <net/netlink.h>
10#include <net/genetlink.h>
11
12static const struct genl_multicast_group quota_mcgrps[] = {
13	{ .name = "events", },
14};
15
16/* Netlink family structure for quota */
17static struct genl_family quota_genl_family = {
18	/*
19	 * Needed due to multicast group ID abuse - old code assumed
20	 * the family ID was also a valid multicast group ID (which
21	 * isn't true) and userspace might thus rely on it. Assign a
22	 * static ID for this group to make dealing with that easier.
23	 */
24	.id = GENL_ID_VFS_DQUOT,
25	.hdrsize = 0,
26	.name = "VFS_DQUOT",
27	.version = 1,
28	.maxattr = QUOTA_NL_A_MAX,
29	.mcgrps = quota_mcgrps,
30	.n_mcgrps = ARRAY_SIZE(quota_mcgrps),
31};
32
33/**
34 * quota_send_warning - Send warning to userspace about exceeded quota
35 * @qid: The kernel internal quota identifier.
36 * @dev: The device on which the fs is mounted (sb->s_dev)
37 * @warntype: The type of the warning: QUOTA_NL_...
38 *
39 * This can be used by filesystems (including those which don't use
40 * dquot) to send a message to userspace relating to quota limits.
41 *
42 */
43
44void quota_send_warning(struct kqid qid, dev_t dev,
45			const char warntype)
46{
47	static atomic_t seq;
48	struct sk_buff *skb;
49	void *msg_head;
50	int ret;
51	int msg_size = 4 * nla_total_size(sizeof(u32)) +
52		       2 * nla_total_size(sizeof(u64));
53
54	/* We have to allocate using GFP_NOFS as we are called from a
55	 * filesystem performing write and thus further recursion into
56	 * the fs to free some data could cause deadlocks. */
57	skb = genlmsg_new(msg_size, GFP_NOFS);
58	if (!skb) {
59		printk(KERN_ERR
60		  "VFS: Not enough memory to send quota warning.\n");
61		return;
62	}
63	msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
64			&quota_genl_family, 0, QUOTA_NL_C_WARNING);
65	if (!msg_head) {
66		printk(KERN_ERR
67		  "VFS: Cannot store netlink header in quota warning.\n");
68		goto err_out;
69	}
70	ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
71	if (ret)
72		goto attr_err_out;
73	ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID,
74			  from_kqid_munged(&init_user_ns, qid));
75	if (ret)
76		goto attr_err_out;
77	ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
78	if (ret)
79		goto attr_err_out;
80	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
81	if (ret)
82		goto attr_err_out;
83	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
84	if (ret)
85		goto attr_err_out;
86	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID,
87			  from_kuid_munged(&init_user_ns, current_uid()));
88	if (ret)
89		goto attr_err_out;
90	genlmsg_end(skb, msg_head);
91
92	genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);
93	return;
94attr_err_out:
95	printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
96err_out:
97	kfree_skb(skb);
98}
99EXPORT_SYMBOL(quota_send_warning);
100
101static int __init quota_init(void)
102{
103	if (genl_register_family(&quota_genl_family) != 0)
104		printk(KERN_ERR
105		       "VFS: Failed to create quota netlink interface.\n");
106	return 0;
107};
108
109module_init(quota_init);
110