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 "a_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("a_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("a_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); 104