drivers/connector/connector.c

   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 int cn_init(void)
 252 {
 253         struct cn_dev *dev = &cdev;
 254         struct netlink_kernel_cfg cfg = {
 255                 .groups = CN_NETLINK_USERS + 0xf,
 256                 .input  = cn_rx_skb,
 257         };
 258
 259         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
 260         if (!dev->nls)
 261                 return -EIO;
 262
 263         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 264         if (!dev->cbdev) {
 265                 netlink_kernel_release(dev->nls);
 266                 return -EINVAL;
 267         }
 268
 269         cn_already_initialized = 1;
 270
 271         proc_create_single("connector", S_IRUGO, init_net.proc_net, cn_proc_show);
 272
 273         return 0;
 274 }
 275
 276 static void cn_fini(void)
 277 {
 278         struct cn_dev *dev = &cdev;
 279
 280         cn_already_initialized = 0;
 281
 282         remove_proc_entry("connector", init_net.proc_net);
 283
 284         cn_queue_free_dev(dev->cbdev);
 285         netlink_kernel_release(dev->nls);
 286 }
 287
 288 subsys_initcall(cn_init);
 289 module_exit(cn_fini);