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, 0, 0, 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] " 113 "(%u vs %zu)", tfr->request_type, 114 tfr->data_size, *(pkg->data_size)); 115 116 *(pkg->data_size) = 0; 117 pkg->error = -ENOSPC; 118 } else { 119 pkg->error = tfr->error; 120 memcpy(pkg->data, tfr->data, tfr->data_size); 121 *(pkg->data_size) = tfr->data_size; 122 } 123 complete(&pkg->complete); 124 return 0; 125 } 126 127 return -ENOENT; 128 } 129 130 /* 131 * This is the connector callback that delivers data 132 * that was sent from userspace. 133 */ 134 static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp) 135 { 136 struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1); 137 138 if (!capable(CAP_SYS_ADMIN)) 139 return; 140 141 spin_lock(&receiving_list_lock); 142 if (msg->len == 0) 143 fill_pkg(msg, NULL); 144 else if (msg->len < sizeof(*tfr)) 145 DMERR("Incomplete message received (expected %u, got %u): [%u]", 146 (unsigned)sizeof(*tfr), msg->len, msg->seq); 147 else 148 fill_pkg(NULL, tfr); 149 spin_unlock(&receiving_list_lock); 150 } 151 152 /** 153 * dm_consult_userspace 154 * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size) 155 * @luid: log's local unique identifier 156 * @request_type: found in include/linux/dm-log-userspace.h 157 * @data: data to tx to the server 158 * @data_size: size of data in bytes 159 * @rdata: place to put return data from server 160 * @rdata_size: value-result (amount of space given/amount of space used) 161 * 162 * rdata_size is undefined on failure. 163 * 164 * Memory used to communicate with userspace is zero'ed 165 * before populating to ensure that no unwanted bits leak 166 * from kernel space to user-space. All userspace log communications 167 * between kernel and user space go through this function. 168 * 169 * Returns: 0 on success, -EXXX on failure 170 **/ 171 int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type, 172 char *data, size_t data_size, 173 char *rdata, size_t *rdata_size) 174 { 175 int r = 0; 176 unsigned long tmo; 177 size_t dummy = 0; 178 int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg); 179 struct dm_ulog_request *tfr = prealloced_ulog_tfr; 180 struct receiving_pkg pkg; 181 182 /* 183 * Given the space needed to hold the 'struct cn_msg' and 184 * 'struct dm_ulog_request' - do we have enough payload 185 * space remaining? 186 */ 187 if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) { 188 DMINFO("Size of tfr exceeds preallocated size"); 189 return -EINVAL; 190 } 191 192 if (!rdata_size) 193 rdata_size = &dummy; 194 resend: 195 /* 196 * We serialize the sending of requests so we can 197 * use the preallocated space. 198 */ 199 mutex_lock(&dm_ulog_lock); 200 201 memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg)); 202 memcpy(tfr->uuid, uuid, DM_UUID_LEN); 203 tfr->version = DM_ULOG_REQUEST_VERSION; 204 tfr->luid = luid; 205 tfr->seq = dm_ulog_seq++; 206 207 /* 208 * Must be valid request type (all other bits set to 209 * zero). This reserves other bits for possible future 210 * use. 211 */ 212 tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; 213 214 tfr->data_size = data_size; 215 if (data && data_size) 216 memcpy(tfr->data, data, data_size); 217 218 memset(&pkg, 0, sizeof(pkg)); 219 init_completion(&pkg.complete); 220 pkg.seq = tfr->seq; 221 pkg.data_size = rdata_size; 222 pkg.data = rdata; 223 spin_lock(&receiving_list_lock); 224 list_add(&(pkg.list), &receiving_list); 225 spin_unlock(&receiving_list_lock); 226 227 r = dm_ulog_sendto_server(tfr); 228 229 mutex_unlock(&dm_ulog_lock); 230 231 if (r) { 232 DMERR("Unable to send log request [%u] to userspace: %d", 233 request_type, r); 234 spin_lock(&receiving_list_lock); 235 list_del_init(&(pkg.list)); 236 spin_unlock(&receiving_list_lock); 237 238 goto out; 239 } 240 241 tmo = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT); 242 spin_lock(&receiving_list_lock); 243 list_del_init(&(pkg.list)); 244 spin_unlock(&receiving_list_lock); 245 if (!tmo) { 246 DMWARN("[%s] Request timed out: [%u/%u] - retrying", 247 (strlen(uuid) > 8) ? 248 (uuid + (strlen(uuid) - 8)) : (uuid), 249 request_type, pkg.seq); 250 goto resend; 251 } 252 253 r = pkg.error; 254 if (r == -EAGAIN) 255 goto resend; 256 257 out: 258 return r; 259 } 260 261 int dm_ulog_tfr_init(void) 262 { 263 int r; 264 void *prealloced; 265 266 INIT_LIST_HEAD(&receiving_list); 267 268 prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); 269 if (!prealloced) 270 return -ENOMEM; 271 272 prealloced_cn_msg = prealloced; 273 prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); 274 275 r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback); 276 if (r) { 277 kfree(prealloced_cn_msg); 278 return r; 279 } 280 281 return 0; 282 } 283 284 void dm_ulog_tfr_exit(void) 285 { 286 cn_del_callback(&ulog_cn_id); 287 kfree(prealloced_cn_msg); 288 } 289