LXR linux/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
  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