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 
11 static const struct genl_multicast_group quota_mcgrps[] = {
12 	{ .name = "events", },
13 };
14 
15 /* Netlink family structure for quota */
16 static 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 
quota_send_warning(struct kqid qid,dev_t dev,const char warntype)37 void 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;
89 attr_err_out:
90 	printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
91 err_out:
92 	kfree_skb(skb);
93 }
94 EXPORT_SYMBOL(quota_send_warning);
95 
quota_init(void)96 static 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 };
103 fs_initcall(quota_init);
104