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);