fs/quota/netlink.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <linux/cred.h>
0003 #include <linux/init.h>
0004 #include <linux/kernel.h>
0005 #include <linux/quotaops.h>
0006 #include <linux/sched.h>
0007 #include <linux/slab.h>
0008 #include <net/netlink.h>
0009 #include <net/genetlink.h>
0010
0011 static const struct genl_multicast_group quota_mcgrps[] = {
0012     { .name = "events", },
0013 };
0014
0015 /* Netlink family structure for quota */
0016 static struct genl_family quota_genl_family __ro_after_init = {
0017     .module = THIS_MODULE,
0018     .hdrsize = 0,
0019     .name = "VFS_DQUOT",
0020     .version = 1,
0021     .maxattr = QUOTA_NL_A_MAX,
0022     .mcgrps = quota_mcgrps,
0023     .n_mcgrps = ARRAY_SIZE(quota_mcgrps),
0024 };
0025
0026 /**
0027  * quota_send_warning - Send warning to userspace about exceeded quota
0028  * @qid: The kernel internal quota identifier.
0029  * @dev: The device on which the fs is mounted (sb->s_dev)
0030  * @warntype: The type of the warning: QUOTA_NL_...
0031  *
0032  * This can be used by filesystems (including those which don't use
0033  * dquot) to send a message to userspace relating to quota limits.
0034  *
0035  */
0036
0037 void quota_send_warning(struct kqid qid, dev_t dev,
0038             const char warntype)
0039 {
0040     static atomic_t seq;
0041     struct sk_buff *skb;
0042     void *msg_head;
0043     int ret;
0044     int msg_size = 4 * nla_total_size(sizeof(u32)) +
0045                2 * nla_total_size_64bit(sizeof(u64));
0046
0047     /* We have to allocate using GFP_NOFS as we are called from a
0048      * filesystem performing write and thus further recursion into
0049      * the fs to free some data could cause deadlocks. */
0050     skb = genlmsg_new(msg_size, GFP_NOFS);
0051     if (!skb) {
0052         printk(KERN_ERR
0053           "VFS: Not enough memory to send quota warning.\n");
0054         return;
0055     }
0056     msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
0057             &quota_genl_family, 0, QUOTA_NL_C_WARNING);
0058     if (!msg_head) {
0059         printk(KERN_ERR
0060           "VFS: Cannot store netlink header in quota warning.\n");
0061         goto err_out;
0062     }
0063     ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
0064     if (ret)
0065         goto attr_err_out;
0066     ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
0067                 from_kqid_munged(&init_user_ns, qid),
0068                 QUOTA_NL_A_PAD);
0069     if (ret)
0070         goto attr_err_out;
0071     ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
0072     if (ret)
0073         goto attr_err_out;
0074     ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
0075     if (ret)
0076         goto attr_err_out;
0077     ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
0078     if (ret)
0079         goto attr_err_out;
0080     ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
0081                 from_kuid_munged(&init_user_ns, current_uid()),
0082                 QUOTA_NL_A_PAD);
0083     if (ret)
0084         goto attr_err_out;
0085     genlmsg_end(skb, msg_head);
0086
0087     genlmsg_multicast(&quota_genl_family, skb, 0, 0, GFP_NOFS);
0088     return;
0089 attr_err_out:
0090     printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
0091 err_out:
0092     kfree_skb(skb);
0093 }
0094 EXPORT_SYMBOL(quota_send_warning);
0095
0096 static int __init quota_init(void)
0097 {
0098     if (genl_register_family(&quota_genl_family) != 0)
0099         printk(KERN_ERR
0100                "VFS: Failed to create quota netlink interface.\n");
0101     return 0;
0102 };
0103 fs_initcall(quota_init);