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1// SPDX-License-Identifier: GPL-2.0-only2/*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 19static uint32_t dm_ulog_seq;20 21/*22 * Netlink/Connector is an unreliable protocol. How long should23 * 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 discarded25 * 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 speed31 */32#define DM_ULOG_PREALLOCED_SIZE 51233static struct cn_msg *prealloced_cn_msg;34static struct dm_ulog_request *prealloced_ulog_tfr;35 36static struct cb_id ulog_cn_id = {37 .idx = CN_IDX_DM,38 .val = CN_VAL_DM_USERSPACE_LOG39};40 41static DEFINE_MUTEX(dm_ulog_lock);42 43struct 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 54static DEFINE_SPINLOCK(receiving_list_lock);55static struct list_head receiving_list;56 57static 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 not77 * 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 userspace79 * that the request was received.80 *81 * Returns: 0 on success, -ENOENT on failure82 */83static 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 statically90 * allocated on the stack in 'dm_consult_userspace'.91 * Each process that is waiting for a reply from the user92 * space server will have an entry in this list.93 *94 * We are safe to do it this way because the stack space95 * is unique to each process, but still addressable by96 * 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 our106 * storage capacity. Otherwise, along with the107 * 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 data131 * that was sent from userspace.132 */133static 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 int)sizeof(*tfr), msg->len, msg->seq);146 else147 fill_pkg(NULL, tfr);148 spin_unlock(&receiving_list_lock);149}150 151/**152 * dm_consult_userspace153 * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size)154 * @luid: log's local unique identifier155 * @request_type: found in include/linux/dm-log-userspace.h156 * @data: data to tx to the server157 * @data_size: size of data in bytes158 * @rdata: place to put return data from server159 * @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'ed164 * before populating to ensure that no unwanted bits leak165 * from kernel space to user-space. All userspace log communications166 * between kernel and user space go through this function.167 *168 * Returns: 0 on success, -EXXX on failure169 **/170int 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' and183 * 'struct dm_ulog_request' - do we have enough payload184 * 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;193resend:194 /*195 * We serialize the sending of requests so we can196 * 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 to208 * zero). This reserves other bits for possible future209 * 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(&pkg.complete);219 pkg.seq = tfr->seq;220 pkg.data_size = rdata_size;221 pkg.data = rdata;222 spin_lock(&receiving_list_lock);223 list_add(&(pkg.list), &receiving_list);224 spin_unlock(&receiving_list_lock);225 226 r = dm_ulog_sendto_server(tfr);227 228 mutex_unlock(&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(&receiving_list_lock);234 list_del_init(&(pkg.list));235 spin_unlock(&receiving_list_lock);236 237 goto out;238 }239 240 tmo = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT);241 spin_lock(&receiving_list_lock);242 list_del_init(&(pkg.list));243 spin_unlock(&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 256out:257 return r;258}259 260int dm_ulog_tfr_init(void)261{262 int r;263 void *prealloced;264 265 INIT_LIST_HEAD(&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(&ulog_cn_id, "dmlogusr", cn_ulog_callback);275 if (r) {276 kfree(prealloced_cn_msg);277 return r;278 }279 280 return 0;281}282 283void dm_ulog_tfr_exit(void)284{285 cn_del_callback(&ulog_cn_id);286 kfree(prealloced_cn_msg);287}288