// SPDX-License-Identifier: GPL-2.0
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#include <linux/cred.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/quotaops.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include <net/netlink.h>
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#include <net/genetlink.h>
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static const struct genl_multicast_group quota_mcgrps[] = {
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{ .name = "events", },
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};
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/* Netlink family structure for quota */
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static struct genl_family quota_genl_family __ro_after_init = {
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.module = THIS_MODULE,
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.hdrsize = 0,
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.name = "VFS_DQUOT",
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.version = 1,
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.maxattr = QUOTA_NL_A_MAX,
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.mcgrps = quota_mcgrps,
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.n_mcgrps = ARRAY_SIZE(quota_mcgrps),
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};
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/**
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* quota_send_warning - Send warning to userspace about exceeded quota
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* @qid: The kernel internal quota identifier.
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* @dev: The device on which the fs is mounted (sb->s_dev)
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* @warntype: The type of the warning: QUOTA_NL_...
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*
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* This can be used by filesystems (including those which don't use
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* dquot) to send a message to userspace relating to quota limits.
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*
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*/
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void quota_send_warning(struct kqid qid, dev_t dev,
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const char warntype)
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{
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static atomic_t seq;
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struct sk_buff *skb;
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void *msg_head;
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int ret;
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int msg_size = 4 * nla_total_size(sizeof(u32)) +
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2 * nla_total_size_64bit(sizeof(u64));
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/* We have to allocate using GFP_NOFS as we are called from a
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* filesystem performing write and thus further recursion into
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* the fs to free some data could cause deadlocks. */
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skb = genlmsg_new(msg_size, GFP_NOFS);
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if (!skb) {
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printk(KERN_ERR
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"VFS: Not enough memory to send quota warning.\n");
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return;
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}
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msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
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"a_genl_family, 0, QUOTA_NL_C_WARNING);
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if (!msg_head) {
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printk(KERN_ERR
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"VFS: Cannot store netlink header in quota warning.\n");
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goto err_out;
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}
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ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, qid.type);
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if (ret)
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goto attr_err_out;
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ret = nla_put_u64_64bit(skb, QUOTA_NL_A_EXCESS_ID,
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from_kqid_munged(&init_user_ns, qid),
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QUOTA_NL_A_PAD);
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if (ret)
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goto attr_err_out;
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ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
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if (ret)
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goto attr_err_out;
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ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR, MAJOR(dev));
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if (ret)
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goto attr_err_out;
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ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR, MINOR(dev));
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if (ret)
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goto attr_err_out;
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ret = nla_put_u64_64bit(skb, QUOTA_NL_A_CAUSED_ID,
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from_kuid_munged(&init_user_ns, current_uid()),
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QUOTA_NL_A_PAD);
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if (ret)
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goto attr_err_out;
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genlmsg_end(skb, msg_head);
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genlmsg_multicast("a_genl_family, skb, 0, 0, GFP_NOFS);
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return;
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attr_err_out:
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printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
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err_out:
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kfree_skb(skb);
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}
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EXPORT_SYMBOL(quota_send_warning);
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static int __init quota_init(void)
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{
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if (genl_register_family("a_genl_family) != 0)
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printk(KERN_ERR
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"VFS: Failed to create quota netlink interface.\n");
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return 0;
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};
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fs_initcall(quota_init);
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