1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * connector.c 4 * 5 * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net> 6 * All rights reserved. 7 */ 8 9 #include <linux/compiler.h> 10 #include <linux/kernel.h> 11 #include <linux/module.h> 12 #include <linux/list.h> 13 #include <linux/skbuff.h> 14 #include <net/netlink.h> 15 #include <linux/moduleparam.h> 16 #include <linux/connector.h> 17 #include <linux/slab.h> 18 #include <linux/mutex.h> 19 #include <linux/proc_fs.h> 20 #include <linux/spinlock.h> 21 22 #include <net/sock.h> 23 24 MODULE_LICENSE("GPL"); 25 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>"); 26 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector."); 27 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR); 28 29 static struct cn_dev cdev; 30 31 static int cn_already_initialized; 32 33 /* 34 * Sends mult (multiple) cn_msg at a time. 35 * 36 * msg->seq and msg->ack are used to determine message genealogy. 37 * When someone sends message it puts there locally unique sequence 38 * and random acknowledge numbers. Sequence number may be copied into 39 * nlmsghdr->nlmsg_seq too. 40 * 41 * Sequence number is incremented with each message to be sent. 42 * 43 * If we expect a reply to our message then the sequence number in 44 * received message MUST be the same as in original message, and 45 * acknowledge number MUST be the same + 1. 46 * 47 * If we receive a message and its sequence number is not equal to the 48 * one we are expecting then it is a new message. 49 * 50 * If we receive a message and its sequence number is the same as one 51 * we are expecting but it's acknowledgement number is not equal to 52 * the acknowledgement number in the original message + 1, then it is 53 * a new message. 54 * 55 * If msg->len != len, then additional cn_msg messages are expected following 56 * the first msg. 57 * 58 * The message is sent to, the portid if given, the group if given, both if 59 * both, or if both are zero then the group is looked up and sent there. 60 */ 61 int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 __group, 62 gfp_t gfp_mask, netlink_filter_fn filter, 63 void *filter_data) 64 { 65 struct cn_callback_entry *__cbq; 66 unsigned int size; 67 struct sk_buff *skb; 68 struct nlmsghdr *nlh; 69 struct cn_msg *data; 70 struct cn_dev *dev = &cdev; 71 u32 group = 0; 72 int found = 0; 73 74 if (portid || __group) { 75 group = __group; 76 } else { 77 spin_lock_bh(&dev->cbdev->queue_lock); 78 list_for_each_entry(__cbq, &dev->cbdev->queue_list, 79 callback_entry) { 80 if (cn_cb_equal(&__cbq->id.id, &msg->id)) { 81 found = 1; 82 group = __cbq->group; 83 break; 84 } 85 } 86 spin_unlock_bh(&dev->cbdev->queue_lock); 87 88 if (!found) 89 return -ENODEV; 90 } 91 92 if (!portid && !netlink_has_listeners(dev->nls, group)) 93 return -ESRCH; 94 95 size = sizeof(*msg) + len; 96 97 skb = nlmsg_new(size, gfp_mask); 98 if (!skb) 99 return -ENOMEM; 100 101 nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0); 102 if (!nlh) { 103 kfree_skb(skb); 104 return -EMSGSIZE; 105 } 106 107 data = nlmsg_data(nlh); 108 109 memcpy(data, msg, size); 110 111 NETLINK_CB(skb).dst_group = group; 112 113 if (group) 114 return netlink_broadcast_filtered(dev->nls, skb, portid, group, 115 gfp_mask, filter, 116 (void *)filter_data); 117 return netlink_unicast(dev->nls, skb, portid, 118 !gfpflags_allow_blocking(gfp_mask)); 119 } 120 EXPORT_SYMBOL_GPL(cn_netlink_send_mult); 121 122 /* same as cn_netlink_send_mult except msg->len is used for len */ 123 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group, 124 gfp_t gfp_mask) 125 { 126 return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask, 127 NULL, NULL); 128 } 129 EXPORT_SYMBOL_GPL(cn_netlink_send); 130 131 /* 132 * Callback helper - queues work and setup destructor for given data. 133 */ 134 static int cn_call_callback(struct sk_buff *skb) 135 { 136 struct nlmsghdr *nlh; 137 struct cn_callback_entry *i, *cbq = NULL; 138 struct cn_dev *dev = &cdev; 139 struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb)); 140 struct netlink_skb_parms *nsp = &NETLINK_CB(skb); 141 int err = -ENODEV; 142 143 /* verify msg->len is within skb */ 144 nlh = nlmsg_hdr(skb); 145 if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len) 146 return -EINVAL; 147 148 spin_lock_bh(&dev->cbdev->queue_lock); 149 list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) { 150 if (cn_cb_equal(&i->id.id, &msg->id)) { 151 refcount_inc(&i->refcnt); 152 cbq = i; 153 break; 154 } 155 } 156 spin_unlock_bh(&dev->cbdev->queue_lock); 157 158 if (cbq != NULL) { 159 cbq->callback(msg, nsp); 160 kfree_skb(skb); 161 cn_queue_release_callback(cbq); 162 err = 0; 163 } 164 165 return err; 166 } 167 168 /* 169 * Allow non-root access for NETLINK_CONNECTOR family having CN_IDX_PROC 170 * multicast group. 171 */ 172 static int cn_bind(struct net *net, int group) 173 { 174 unsigned long groups = (unsigned long) group; 175 176 if (ns_capable(net->user_ns, CAP_NET_ADMIN)) 177 return 0; 178 179 if (test_bit(CN_IDX_PROC - 1, &groups)) 180 return 0; 181 182 return -EPERM; 183 } 184 185 static void cn_release(struct sock *sk, unsigned long *groups) 186 { 187 if (groups && test_bit(CN_IDX_PROC - 1, groups)) { 188 kfree(sk->sk_user_data); 189 sk->sk_user_data = NULL; 190 } 191 } 192 193 /* 194 * Main netlink receiving function. 195 * 196 * It checks skb, netlink header and msg sizes, and calls callback helper. 197 */ 198 static void cn_rx_skb(struct sk_buff *skb) 199 { 200 struct nlmsghdr *nlh; 201 int len, err; 202 203 if (skb->len >= NLMSG_HDRLEN) { 204 nlh = nlmsg_hdr(skb); 205 len = nlmsg_len(nlh); 206 207 if (len < (int)sizeof(struct cn_msg) || 208 skb->len < nlh->nlmsg_len || 209 len > CONNECTOR_MAX_MSG_SIZE) 210 return; 211 212 err = cn_call_callback(skb_get(skb)); 213 if (err < 0) 214 kfree_skb(skb); 215 } 216 } 217 218 /* 219 * Callback add routing - adds callback with given ID and name. 220 * If there is registered callback with the same ID it will not be added. 221 * 222 * May sleep. 223 */ 224 int cn_add_callback(const struct cb_id *id, const char *name, 225 void (*callback)(struct cn_msg *, 226 struct netlink_skb_parms *)) 227 { 228 struct cn_dev *dev = &cdev; 229 230 if (!cn_already_initialized) 231 return -EAGAIN; 232 233 return cn_queue_add_callback(dev->cbdev, name, id, callback); 234 } 235 EXPORT_SYMBOL_GPL(cn_add_callback); 236 237 /* 238 * Callback remove routing - removes callback 239 * with given ID. 240 * If there is no registered callback with given 241 * ID nothing happens. 242 * 243 * May sleep while waiting for reference counter to become zero. 244 */ 245 void cn_del_callback(const struct cb_id *id) 246 { 247 struct cn_dev *dev = &cdev; 248 249 cn_queue_del_callback(dev->cbdev, id); 250 } 251 EXPORT_SYMBOL_GPL(cn_del_callback); 252 253 static int __maybe_unused cn_proc_show(struct seq_file *m, void *v) 254 { 255 struct cn_queue_dev *dev = cdev.cbdev; 256 struct cn_callback_entry *cbq; 257 258 seq_printf(m, "Name ID\n"); 259 260 spin_lock_bh(&dev->queue_lock); 261 262 list_for_each_entry(cbq, &dev->queue_list, callback_entry) { 263 seq_printf(m, "%-15s %u:%u\n", 264 cbq->id.name, 265 cbq->id.id.idx, 266 cbq->id.id.val); 267 } 268 269 spin_unlock_bh(&dev->queue_lock); 270 271 return 0; 272 } 273 274 static int cn_init(void) 275 { 276 struct cn_dev *dev = &cdev; 277 struct netlink_kernel_cfg cfg = { 278 .groups = CN_NETLINK_USERS + 0xf, 279 .input = cn_rx_skb, 280 .flags = NL_CFG_F_NONROOT_RECV, 281 .bind = cn_bind, 282 .release = cn_release, 283 }; 284 285 dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg); 286 if (!dev->nls) 287 return -EIO; 288 289 dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls); 290 if (!dev->cbdev) { 291 netlink_kernel_release(dev->nls); 292 return -EINVAL; 293 } 294 295 cn_already_initialized = 1; 296 297 proc_create_single("connector", S_IRUGO, init_net.proc_net, cn_proc_show); 298 299 return 0; 300 } 301 302 static void cn_fini(void) 303 { 304 struct cn_dev *dev = &cdev; 305 306 cn_already_initialized = 0; 307 308 remove_proc_entry("connector", init_net.proc_net); 309 310 cn_queue_free_dev(dev->cbdev); 311 netlink_kernel_release(dev->nls); 312 } 313 314 subsys_initcall(cn_init); 315 module_exit(cn_fini); 316