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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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2ecf7536b2
The quota code is abusing the genetlink API and is using its family ID as the multicast group ID, which is invalid and may belong to somebody else (and likely will.) Make the quota code use the correct API, but since this is already used as-is by userspace, reserve a family ID for this code and also reserve that group ID to not break userspace assumptions. Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
111 lines
3.1 KiB
C
111 lines
3.1 KiB
C
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#include <linux/cred.h>
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#include <linux/init.h>
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#include <linux/module.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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/* Netlink family structure for quota */
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static struct genl_family quota_genl_family = {
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/*
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* Needed due to multicast group ID abuse - old code assumed
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* the family ID was also a valid multicast group ID (which
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* isn't true) and userspace might thus rely on it. Assign a
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* static ID for this group to make dealing with that easier.
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*/
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.id = GENL_ID_VFS_DQUOT,
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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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};
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static struct genl_multicast_group quota_mcgrp = {
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.name = "events",
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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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* @type: The quota type: USRQQUOTA, GRPQUOTA,...
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* @id: The user or group id of the quota that was exceeded
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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(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(skb, QUOTA_NL_A_EXCESS_ID,
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from_kqid_munged(&init_user_ns, qid));
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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(skb, QUOTA_NL_A_CAUSED_ID,
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from_kuid_munged(&init_user_ns, current_uid()));
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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(skb, 0, quota_mcgrp.id, 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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if (genl_register_mc_group("a_genl_family, "a_mcgrp))
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printk(KERN_ERR
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"VFS: Failed to register quota mcast group.\n");
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return 0;
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};
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module_init(quota_init);
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