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(payload: sizeof(u32)) + |
45 | 2 * nla_total_size_64bit(payload: 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(payload: 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, portid: 0, seq: atomic_add_return(i: 1, v: &seq), |
57 | family: "a_genl_family, flags: 0, cmd: 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, attrtype: QUOTA_NL_A_QTYPE, value: qid.type); |
64 | if (ret) |
65 | goto attr_err_out; |
66 | ret = nla_put_u64_64bit(skb, attrtype: QUOTA_NL_A_EXCESS_ID, |
67 | value: from_kqid_munged(to: &init_user_ns, qid), |
68 | padattr: QUOTA_NL_A_PAD); |
69 | if (ret) |
70 | goto attr_err_out; |
71 | ret = nla_put_u32(skb, attrtype: QUOTA_NL_A_WARNING, value: warntype); |
72 | if (ret) |
73 | goto attr_err_out; |
74 | ret = nla_put_u32(skb, attrtype: QUOTA_NL_A_DEV_MAJOR, MAJOR(dev)); |
75 | if (ret) |
76 | goto attr_err_out; |
77 | ret = nla_put_u32(skb, attrtype: QUOTA_NL_A_DEV_MINOR, MINOR(dev)); |
78 | if (ret) |
79 | goto attr_err_out; |
80 | ret = nla_put_u64_64bit(skb, attrtype: QUOTA_NL_A_CAUSED_ID, |
81 | value: from_kuid_munged(to: &init_user_ns, current_uid()), |
82 | padattr: QUOTA_NL_A_PAD); |
83 | if (ret) |
84 | goto attr_err_out; |
85 | genlmsg_end(skb, hdr: msg_head); |
86 | |
87 | genlmsg_multicast(family: "a_genl_family, skb, portid: 0, group: 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(family: "a_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 | |