1 /*
2  * Copyright (C) 2006-2009 Red Hat, Inc.
3  *
4  * This file is released under the LGPL.
5  */
6 
7 #include <linux/kernel.h>
8 #include <linux/module.h>
9 #include <linux/slab.h>
10 #include <net/sock.h>
11 #include <linux/workqueue.h>
12 #include <linux/connector.h>
13 #include <linux/device-mapper.h>
14 #include <linux/dm-log-userspace.h>
15 
16 #include "dm-log-userspace-transfer.h"
17 
18 static uint32_t dm_ulog_seq;
19 
20 /*
21  * Netlink/Connector is an unreliable protocol.  How long should
22  * we wait for a response before assuming it was lost and retrying?
23  * (If we do receive a response after this time, it will be discarded
24  * and the response to the resent request will be waited for.
25  */
26 #define DM_ULOG_RETRY_TIMEOUT (15 * HZ)
27 
28 /*
29  * Pre-allocated space for speed
30  */
31 #define DM_ULOG_PREALLOCED_SIZE 512
32 static struct cn_msg *prealloced_cn_msg;
33 static struct dm_ulog_request *prealloced_ulog_tfr;
34 
35 static struct cb_id ulog_cn_id = {
36 	.idx = CN_IDX_DM,
37 	.val = CN_VAL_DM_USERSPACE_LOG
38 };
39 
40 static DEFINE_MUTEX(dm_ulog_lock);
41 
42 struct receiving_pkg {
43 	struct list_head list;
44 	struct completion complete;
45 
46 	uint32_t seq;
47 
48 	int error;
49 	size_t *data_size;
50 	char *data;
51 };
52 
53 static DEFINE_SPINLOCK(receiving_list_lock);
54 static struct list_head receiving_list;
55 
56 static int dm_ulog_sendto_server(struct dm_ulog_request *tfr)
57 {
58 	int r;
59 	struct cn_msg *msg = prealloced_cn_msg;
60 
61 	memset(msg, 0, sizeof(struct cn_msg));
62 
63 	msg->id.idx = ulog_cn_id.idx;
64 	msg->id.val = ulog_cn_id.val;
65 	msg->ack = 0;
66 	msg->seq = tfr->seq;
67 	msg->len = sizeof(struct dm_ulog_request) + tfr->data_size;
68 
69 	r = cn_netlink_send(msg, 0, gfp_any());
70 
71 	return r;
72 }
73 
74 /*
75  * Parameters for this function can be either msg or tfr, but not
76  * both.  This function fills in the reply for a waiting request.
77  * If just msg is given, then the reply is simply an ACK from userspace
78  * that the request was received.
79  *
80  * Returns: 0 on success, -ENOENT on failure
81  */
82 static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr)
83 {
84 	uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0;
85 	struct receiving_pkg *pkg;
86 
87 	/*
88 	 * The 'receiving_pkg' entries in this list are statically
89 	 * allocated on the stack in 'dm_consult_userspace'.
90 	 * Each process that is waiting for a reply from the user
91 	 * space server will have an entry in this list.
92 	 *
93 	 * We are safe to do it this way because the stack space
94 	 * is unique to each process, but still addressable by
95 	 * other processes.
96 	 */
97 	list_for_each_entry(pkg, &receiving_list, list) {
98 		if (rtn_seq != pkg->seq)
99 			continue;
100 
101 		if (msg) {
102 			pkg->error = -msg->ack;
103 			/*
104 			 * If we are trying again, we will need to know our
105 			 * storage capacity.  Otherwise, along with the
106 			 * error code, we make explicit that we have no data.
107 			 */
108 			if (pkg->error != -EAGAIN)
109 				*(pkg->data_size) = 0;
110 		} else if (tfr->data_size > *(pkg->data_size)) {
111 			DMERR("Insufficient space to receive package [%u] "
112 			      "(%u vs %zu)", tfr->request_type,
113 			      tfr->data_size, *(pkg->data_size));
114 
115 			*(pkg->data_size) = 0;
116 			pkg->error = -ENOSPC;
117 		} else {
118 			pkg->error = tfr->error;
119 			memcpy(pkg->data, tfr->data, tfr->data_size);
120 			*(pkg->data_size) = tfr->data_size;
121 		}
122 		complete(&pkg->complete);
123 		return 0;
124 	}
125 
126 	return -ENOENT;
127 }
128 
129 /*
130  * This is the connector callback that delivers data
131  * that was sent from userspace.
132  */
133 static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
134 {
135 	struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);
136 
137 	if (!capable(CAP_SYS_ADMIN))
138 		return;
139 
140 	spin_lock(&receiving_list_lock);
141 	if (msg->len == 0)
142 		fill_pkg(msg, NULL);
143 	else if (msg->len < sizeof(*tfr))
144 		DMERR("Incomplete message received (expected %u, got %u): [%u]",
145 		      (unsigned)sizeof(*tfr), msg->len, msg->seq);
146 	else
147 		fill_pkg(NULL, tfr);
148 	spin_unlock(&receiving_list_lock);
149 }
150 
151 /**
152  * dm_consult_userspace
153  * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)
154  * @luid: log's local unique identifier
155  * @request_type:  found in include/linux/dm-log-userspace.h
156  * @data: data to tx to the server
157  * @data_size: size of data in bytes
158  * @rdata: place to put return data from server
159  * @rdata_size: value-result (amount of space given/amount of space used)
160  *
161  * rdata_size is undefined on failure.
162  *
163  * Memory used to communicate with userspace is zero'ed
164  * before populating to ensure that no unwanted bits leak
165  * from kernel space to user-space.  All userspace log communications
166  * between kernel and user space go through this function.
167  *
168  * Returns: 0 on success, -EXXX on failure
169  **/
170 int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type,
171 			 char *data, size_t data_size,
172 			 char *rdata, size_t *rdata_size)
173 {
174 	int r = 0;
175 	size_t dummy = 0;
176 	int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg);
177 	struct dm_ulog_request *tfr = prealloced_ulog_tfr;
178 	struct receiving_pkg pkg;
179 
180 	/*
181 	 * Given the space needed to hold the 'struct cn_msg' and
182 	 * 'struct dm_ulog_request' - do we have enough payload
183 	 * space remaining?
184 	 */
185 	if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) {
186 		DMINFO("Size of tfr exceeds preallocated size");
187 		return -EINVAL;
188 	}
189 
190 	if (!rdata_size)
191 		rdata_size = &dummy;
192 resend:
193 	/*
194 	 * We serialize the sending of requests so we can
195 	 * use the preallocated space.
196 	 */
197 	mutex_lock(&dm_ulog_lock);
198 
199 	memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg));
200 	memcpy(tfr->uuid, uuid, DM_UUID_LEN);
201 	tfr->version = DM_ULOG_REQUEST_VERSION;
202 	tfr->luid = luid;
203 	tfr->seq = dm_ulog_seq++;
204 
205 	/*
206 	 * Must be valid request type (all other bits set to
207 	 * zero).  This reserves other bits for possible future
208 	 * use.
209 	 */
210 	tfr->request_type = request_type & DM_ULOG_REQUEST_MASK;
211 
212 	tfr->data_size = data_size;
213 	if (data && data_size)
214 		memcpy(tfr->data, data, data_size);
215 
216 	memset(&pkg, 0, sizeof(pkg));
217 	init_completion(&pkg.complete);
218 	pkg.seq = tfr->seq;
219 	pkg.data_size = rdata_size;
220 	pkg.data = rdata;
221 	spin_lock(&receiving_list_lock);
222 	list_add(&(pkg.list), &receiving_list);
223 	spin_unlock(&receiving_list_lock);
224 
225 	r = dm_ulog_sendto_server(tfr);
226 
227 	mutex_unlock(&dm_ulog_lock);
228 
229 	if (r) {
230 		DMERR("Unable to send log request [%u] to userspace: %d",
231 		      request_type, r);
232 		spin_lock(&receiving_list_lock);
233 		list_del_init(&(pkg.list));
234 		spin_unlock(&receiving_list_lock);
235 
236 		goto out;
237 	}
238 
239 	r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);
240 	spin_lock(&receiving_list_lock);
241 	list_del_init(&(pkg.list));
242 	spin_unlock(&receiving_list_lock);
243 	if (!r) {
244 		DMWARN("[%s] Request timed out: [%u/%u] - retrying",
245 		       (strlen(uuid) > 8) ?
246 		       (uuid + (strlen(uuid) - 8)) : (uuid),
247 		       request_type, pkg.seq);
248 		goto resend;
249 	}
250 
251 	r = pkg.error;
252 	if (r == -EAGAIN)
253 		goto resend;
254 
255 out:
256 	return r;
257 }
258 
259 int dm_ulog_tfr_init(void)
260 {
261 	int r;
262 	void *prealloced;
263 
264 	INIT_LIST_HEAD(&receiving_list);
265 
266 	prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL);
267 	if (!prealloced)
268 		return -ENOMEM;
269 
270 	prealloced_cn_msg = prealloced;
271 	prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg);
272 
273 	r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback);
274 	if (r) {
275 		cn_del_callback(&ulog_cn_id);
276 		return r;
277 	}
278 
279 	return 0;
280 }
281 
282 void dm_ulog_tfr_exit(void)
283 {
284 	cn_del_callback(&ulog_cn_id);
285 	kfree(prealloced_cn_msg);
286 }
287