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) 63 { 64 struct cn_callback_entry *__cbq; 65 unsigned int size; 66 struct sk_buff *skb; 67 struct nlmsghdr *nlh; 68 struct cn_msg *data; 69 struct cn_dev *dev = &cdev; 70 u32 group = 0; 71 int found = 0; 72 73 if (portid || __group) { 74 group = __group; 75 } else { 76 spin_lock_bh(&dev->cbdev->queue_lock); 77 list_for_each_entry(__cbq, &dev->cbdev->queue_list, 78 callback_entry) { 79 if (cn_cb_equal(&__cbq->id.id, &msg->id)) { 80 found = 1; 81 group = __cbq->group; 82 break; 83 } 84 } 85 spin_unlock_bh(&dev->cbdev->queue_lock); 86 87 if (!found) 88 return -ENODEV; 89 } 90 91 if (!portid && !netlink_has_listeners(dev->nls, group)) 92 return -ESRCH; 93 94 size = sizeof(*msg) + len; 95 96 skb = nlmsg_new(size, gfp_mask); 97 if (!skb) 98 return -ENOMEM; 99 100 nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0); 101 if (!nlh) { 102 kfree_skb(skb); 103 return -EMSGSIZE; 104 } 105 106 data = nlmsg_data(nlh); 107 108 memcpy(data, msg, size); 109 110 NETLINK_CB(skb).dst_group = group; 111 112 if (group) 113 return netlink_broadcast(dev->nls, skb, portid, group, 114 gfp_mask); 115 return netlink_unicast(dev->nls, skb, portid, 116 !gfpflags_allow_blocking(gfp_mask)); 117 } 118 EXPORT_SYMBOL_GPL(cn_netlink_send_mult); 119 120 /* same as cn_netlink_send_mult except msg->len is used for len */ 121 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group, 122 gfp_t gfp_mask) 123 { 124 return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask); 125 } 126 EXPORT_SYMBOL_GPL(cn_netlink_send); 127 128 /* 129 * Callback helper - queues work and setup destructor for given data. 130 */ 131 static int cn_call_callback(struct sk_buff *skb) 132 { 133 struct nlmsghdr *nlh; 134 struct cn_callback_entry *i, *cbq = NULL; 135 struct cn_dev *dev = &cdev; 136 struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb)); 137 struct netlink_skb_parms *nsp = &NETLINK_CB(skb); 138 int err = -ENODEV; 139 140 /* verify msg->len is within skb */ 141 nlh = nlmsg_hdr(skb); 142 if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len) 143 return -EINVAL; 144 145 spin_lock_bh(&dev->cbdev->queue_lock); 146 list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) { 147 if (cn_cb_equal(&i->id.id, &msg->id)) { 148 refcount_inc(&i->refcnt); 149 cbq = i; 150 break; 151 } 152 } 153 spin_unlock_bh(&dev->cbdev->queue_lock); 154 155 if (cbq != NULL) { 156 cbq->callback(msg, nsp); 157 kfree_skb(skb); 158 cn_queue_release_callback(cbq); 159 err = 0; 160 } 161 162 return err; 163 } 164 165 /* 166 * Main netlink receiving function. 167 * 168 * It checks skb, netlink header and msg sizes, and calls callback helper. 169 */ 170 static void cn_rx_skb(struct sk_buff *skb) 171 { 172 struct nlmsghdr *nlh; 173 int len, err; 174 175 if (skb->len >= NLMSG_HDRLEN) { 176 nlh = nlmsg_hdr(skb); 177 len = nlmsg_len(nlh); 178 179 if (len < (int)sizeof(struct cn_msg) || 180 skb->len < nlh->nlmsg_len || 181 len > CONNECTOR_MAX_MSG_SIZE) 182 return; 183 184 err = cn_call_callback(skb_get(skb)); 185 if (err < 0) 186 kfree_skb(skb); 187 } 188 } 189 190 /* 191 * Callback add routing - adds callback with given ID and name. 192 * If there is registered callback with the same ID it will not be added. 193 * 194 * May sleep. 195 */ 196 int cn_add_callback(struct cb_id *id, const char *name, 197 void (*callback)(struct cn_msg *, 198 struct netlink_skb_parms *)) 199 { 200 int err; 201 struct cn_dev *dev = &cdev; 202 203 if (!cn_already_initialized) 204 return -EAGAIN; 205 206 err = cn_queue_add_callback(dev->cbdev, name, id, callback); 207 if (err) 208 return err; 209 210 return 0; 211 } 212 EXPORT_SYMBOL_GPL(cn_add_callback); 213 214 /* 215 * Callback remove routing - removes callback 216 * with given ID. 217 * If there is no registered callback with given 218 * ID nothing happens. 219 * 220 * May sleep while waiting for reference counter to become zero. 221 */ 222 void cn_del_callback(struct cb_id *id) 223 { 224 struct cn_dev *dev = &cdev; 225 226 cn_queue_del_callback(dev->cbdev, id); 227 } 228 EXPORT_SYMBOL_GPL(cn_del_callback); 229 230 static int __maybe_unused cn_proc_show(struct seq_file *m, void *v) 231 { 232 struct cn_queue_dev *dev = cdev.cbdev; 233 struct cn_callback_entry *cbq; 234 235 seq_printf(m, "Name ID\n"); 236 237 spin_lock_bh(&dev->queue_lock); 238 239 list_for_each_entry(cbq, &dev->queue_list, callback_entry) { 240 seq_printf(m, "%-15s %u:%u\n", 241 cbq->id.name, 242 cbq->id.id.idx, 243 cbq->id.id.val); 244 } 245 246 spin_unlock_bh(&dev->queue_lock); 247 248 return 0; 249 } 250 251 static struct cn_dev cdev = { 252 .input = cn_rx_skb, 253 }; 254 255 static int cn_init(void) 256 { 257 struct cn_dev *dev = &cdev; 258 struct netlink_kernel_cfg cfg = { 259 .groups = CN_NETLINK_USERS + 0xf, 260 .input = dev->input, 261 }; 262 263 dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg); 264 if (!dev->nls) 265 return -EIO; 266 267 dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls); 268 if (!dev->cbdev) { 269 netlink_kernel_release(dev->nls); 270 return -EINVAL; 271 } 272 273 cn_already_initialized = 1; 274 275 proc_create_single("connector", S_IRUGO, init_net.proc_net, cn_proc_show); 276 277 return 0; 278 } 279 280 static void cn_fini(void) 281 { 282 struct cn_dev *dev = &cdev; 283 284 cn_already_initialized = 0; 285 286 remove_proc_entry("connector", init_net.proc_net); 287 288 cn_queue_free_dev(dev->cbdev); 289 netlink_kernel_release(dev->nls); 290 } 291 292 subsys_initcall(cn_init); 293 module_exit(cn_fini); 294