1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Copyright (C) 2006-2009 Red Hat, Inc. |
4 | * |
5 | * This file is released under the LGPL. |
6 | */ |
7 | |
8 | #include <linux/kernel.h> |
9 | #include <linux/module.h> |
10 | #include <linux/slab.h> |
11 | #include <net/sock.h> |
12 | #include <linux/workqueue.h> |
13 | #include <linux/connector.h> |
14 | #include <linux/device-mapper.h> |
15 | #include <linux/dm-log-userspace.h> |
16 | |
17 | #include "dm-log-userspace-transfer.h" |
18 | |
19 | static uint32_t dm_ulog_seq; |
20 | |
21 | /* |
22 | * Netlink/Connector is an unreliable protocol. How long should |
23 | * we wait for a response before assuming it was lost and retrying? |
24 | * (If we do receive a response after this time, it will be discarded |
25 | * and the response to the resent request will be waited for. |
26 | */ |
27 | #define DM_ULOG_RETRY_TIMEOUT (15 * HZ) |
28 | |
29 | /* |
30 | * Pre-allocated space for speed |
31 | */ |
32 | #define DM_ULOG_PREALLOCED_SIZE 512 |
33 | static struct cn_msg *prealloced_cn_msg; |
34 | static struct dm_ulog_request *prealloced_ulog_tfr; |
35 | |
36 | static struct cb_id ulog_cn_id = { |
37 | .idx = CN_IDX_DM, |
38 | .val = CN_VAL_DM_USERSPACE_LOG |
39 | }; |
40 | |
41 | static DEFINE_MUTEX(dm_ulog_lock); |
42 | |
43 | struct receiving_pkg { |
44 | struct list_head list; |
45 | struct completion complete; |
46 | |
47 | uint32_t seq; |
48 | |
49 | int error; |
50 | size_t *data_size; |
51 | char *data; |
52 | }; |
53 | |
54 | static DEFINE_SPINLOCK(receiving_list_lock); |
55 | static struct list_head receiving_list; |
56 | |
57 | static int dm_ulog_sendto_server(struct dm_ulog_request *tfr) |
58 | { |
59 | int r; |
60 | struct cn_msg *msg = prealloced_cn_msg; |
61 | |
62 | memset(msg, 0, sizeof(struct cn_msg)); |
63 | |
64 | msg->id.idx = ulog_cn_id.idx; |
65 | msg->id.val = ulog_cn_id.val; |
66 | msg->ack = 0; |
67 | msg->seq = tfr->seq; |
68 | msg->len = sizeof(struct dm_ulog_request) + tfr->data_size; |
69 | |
70 | r = cn_netlink_send(msg, portid: 0, group: 0, gfp_mask: gfp_any()); |
71 | |
72 | return r; |
73 | } |
74 | |
75 | /* |
76 | * Parameters for this function can be either msg or tfr, but not |
77 | * both. This function fills in the reply for a waiting request. |
78 | * If just msg is given, then the reply is simply an ACK from userspace |
79 | * that the request was received. |
80 | * |
81 | * Returns: 0 on success, -ENOENT on failure |
82 | */ |
83 | static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr) |
84 | { |
85 | uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0; |
86 | struct receiving_pkg *pkg; |
87 | |
88 | /* |
89 | * The 'receiving_pkg' entries in this list are statically |
90 | * allocated on the stack in 'dm_consult_userspace'. |
91 | * Each process that is waiting for a reply from the user |
92 | * space server will have an entry in this list. |
93 | * |
94 | * We are safe to do it this way because the stack space |
95 | * is unique to each process, but still addressable by |
96 | * other processes. |
97 | */ |
98 | list_for_each_entry(pkg, &receiving_list, list) { |
99 | if (rtn_seq != pkg->seq) |
100 | continue; |
101 | |
102 | if (msg) { |
103 | pkg->error = -msg->ack; |
104 | /* |
105 | * If we are trying again, we will need to know our |
106 | * storage capacity. Otherwise, along with the |
107 | * error code, we make explicit that we have no data. |
108 | */ |
109 | if (pkg->error != -EAGAIN) |
110 | *(pkg->data_size) = 0; |
111 | } else if (tfr->data_size > *(pkg->data_size)) { |
112 | DMERR("Insufficient space to receive package [%u] (%u vs %zu)" , |
113 | tfr->request_type, 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(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 int)sizeof(*tfr), msg->len, msg->seq); |
146 | else |
147 | fill_pkg(NULL, tfr); |
148 | spin_unlock(lock: &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 | unsigned long tmo; |
176 | size_t dummy = 0; |
177 | int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg); |
178 | struct dm_ulog_request *tfr = prealloced_ulog_tfr; |
179 | struct receiving_pkg pkg; |
180 | |
181 | /* |
182 | * Given the space needed to hold the 'struct cn_msg' and |
183 | * 'struct dm_ulog_request' - do we have enough payload |
184 | * space remaining? |
185 | */ |
186 | if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) { |
187 | DMINFO("Size of tfr exceeds preallocated size" ); |
188 | return -EINVAL; |
189 | } |
190 | |
191 | if (!rdata_size) |
192 | rdata_size = &dummy; |
193 | resend: |
194 | /* |
195 | * We serialize the sending of requests so we can |
196 | * use the preallocated space. |
197 | */ |
198 | mutex_lock(&dm_ulog_lock); |
199 | |
200 | memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg)); |
201 | memcpy(tfr->uuid, uuid, DM_UUID_LEN); |
202 | tfr->version = DM_ULOG_REQUEST_VERSION; |
203 | tfr->luid = luid; |
204 | tfr->seq = dm_ulog_seq++; |
205 | |
206 | /* |
207 | * Must be valid request type (all other bits set to |
208 | * zero). This reserves other bits for possible future |
209 | * use. |
210 | */ |
211 | tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; |
212 | |
213 | tfr->data_size = data_size; |
214 | if (data && data_size) |
215 | memcpy(tfr->data, data, data_size); |
216 | |
217 | memset(&pkg, 0, sizeof(pkg)); |
218 | init_completion(x: &pkg.complete); |
219 | pkg.seq = tfr->seq; |
220 | pkg.data_size = rdata_size; |
221 | pkg.data = rdata; |
222 | spin_lock(lock: &receiving_list_lock); |
223 | list_add(new: &(pkg.list), head: &receiving_list); |
224 | spin_unlock(lock: &receiving_list_lock); |
225 | |
226 | r = dm_ulog_sendto_server(tfr); |
227 | |
228 | mutex_unlock(lock: &dm_ulog_lock); |
229 | |
230 | if (r) { |
231 | DMERR("Unable to send log request [%u] to userspace: %d" , |
232 | request_type, r); |
233 | spin_lock(lock: &receiving_list_lock); |
234 | list_del_init(entry: &(pkg.list)); |
235 | spin_unlock(lock: &receiving_list_lock); |
236 | |
237 | goto out; |
238 | } |
239 | |
240 | tmo = wait_for_completion_timeout(x: &(pkg.complete), DM_ULOG_RETRY_TIMEOUT); |
241 | spin_lock(lock: &receiving_list_lock); |
242 | list_del_init(entry: &(pkg.list)); |
243 | spin_unlock(lock: &receiving_list_lock); |
244 | if (!tmo) { |
245 | DMWARN("[%s] Request timed out: [%u/%u] - retrying" , |
246 | (strlen(uuid) > 8) ? |
247 | (uuid + (strlen(uuid) - 8)) : (uuid), |
248 | request_type, pkg.seq); |
249 | goto resend; |
250 | } |
251 | |
252 | r = pkg.error; |
253 | if (r == -EAGAIN) |
254 | goto resend; |
255 | |
256 | out: |
257 | return r; |
258 | } |
259 | |
260 | int dm_ulog_tfr_init(void) |
261 | { |
262 | int r; |
263 | void *prealloced; |
264 | |
265 | INIT_LIST_HEAD(list: &receiving_list); |
266 | |
267 | prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); |
268 | if (!prealloced) |
269 | return -ENOMEM; |
270 | |
271 | prealloced_cn_msg = prealloced; |
272 | prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); |
273 | |
274 | r = cn_add_callback(id: &ulog_cn_id, name: "dmlogusr" , callback: cn_ulog_callback); |
275 | if (r) { |
276 | kfree(objp: prealloced_cn_msg); |
277 | return r; |
278 | } |
279 | |
280 | return 0; |
281 | } |
282 | |
283 | void dm_ulog_tfr_exit(void) |
284 | { |
285 | cn_del_callback(id: &ulog_cn_id); |
286 | kfree(objp: prealloced_cn_msg); |
287 | } |
288 | |