GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / quota / netlink.c
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
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
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);