1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/fs/nfs/namespace.c 4 * 5 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com> 6 * - Modified by David Howells <dhowells@redhat.com> 7 * 8 * NFS namespace 9 */ 10 11 #include <linux/module.h> 12 #include <linux/dcache.h> 13 #include <linux/gfp.h> 14 #include <linux/mount.h> 15 #include <linux/namei.h> 16 #include <linux/nfs_fs.h> 17 #include <linux/string.h> 18 #include <linux/sunrpc/clnt.h> 19 #include <linux/vfs.h> 20 #include <linux/sunrpc/gss_api.h> 21 #include "internal.h" 22 #include "nfs.h" 23 24 #define NFSDBG_FACILITY NFSDBG_VFS 25 26 static void nfs_expire_automounts(struct work_struct *work); 27 28 static LIST_HEAD(nfs_automount_list); 29 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 30 int nfs_mountpoint_expiry_timeout = 500 * HZ; 31 32 /* 33 * nfs_path - reconstruct the path given an arbitrary dentry 34 * @base - used to return pointer to the end of devname part of path 35 * @dentry - pointer to dentry 36 * @buffer - result buffer 37 * @buflen - length of buffer 38 * @flags - options (see below) 39 * 40 * Helper function for constructing the server pathname 41 * by arbitrary hashed dentry. 42 * 43 * This is mainly for use in figuring out the path on the 44 * server side when automounting on top of an existing partition 45 * and in generating /proc/mounts and friends. 46 * 47 * Supported flags: 48 * NFS_PATH_CANONICAL: ensure there is exactly one slash after 49 * the original device (export) name 50 * (if unset, the original name is returned verbatim) 51 */ 52 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen, 53 unsigned flags) 54 { 55 char *end; 56 int namelen; 57 unsigned seq; 58 const char *base; 59 60 rename_retry: 61 end = buffer+buflen; 62 *--end = '\0'; 63 buflen--; 64 65 seq = read_seqbegin(&rename_lock); 66 rcu_read_lock(); 67 while (1) { 68 spin_lock(&dentry->d_lock); 69 if (IS_ROOT(dentry)) 70 break; 71 namelen = dentry->d_name.len; 72 buflen -= namelen + 1; 73 if (buflen < 0) 74 goto Elong_unlock; 75 end -= namelen; 76 memcpy(end, dentry->d_name.name, namelen); 77 *--end = '/'; 78 spin_unlock(&dentry->d_lock); 79 dentry = dentry->d_parent; 80 } 81 if (read_seqretry(&rename_lock, seq)) { 82 spin_unlock(&dentry->d_lock); 83 rcu_read_unlock(); 84 goto rename_retry; 85 } 86 if ((flags & NFS_PATH_CANONICAL) && *end != '/') { 87 if (--buflen < 0) { 88 spin_unlock(&dentry->d_lock); 89 rcu_read_unlock(); 90 goto Elong; 91 } 92 *--end = '/'; 93 } 94 *p = end; 95 base = dentry->d_fsdata; 96 if (!base) { 97 spin_unlock(&dentry->d_lock); 98 rcu_read_unlock(); 99 WARN_ON(1); 100 return end; 101 } 102 namelen = strlen(base); 103 if (*end == '/') { 104 /* Strip off excess slashes in base string */ 105 while (namelen > 0 && base[namelen - 1] == '/') 106 namelen--; 107 } 108 buflen -= namelen; 109 if (buflen < 0) { 110 spin_unlock(&dentry->d_lock); 111 rcu_read_unlock(); 112 goto Elong; 113 } 114 end -= namelen; 115 memcpy(end, base, namelen); 116 spin_unlock(&dentry->d_lock); 117 rcu_read_unlock(); 118 return end; 119 Elong_unlock: 120 spin_unlock(&dentry->d_lock); 121 rcu_read_unlock(); 122 if (read_seqretry(&rename_lock, seq)) 123 goto rename_retry; 124 Elong: 125 return ERR_PTR(-ENAMETOOLONG); 126 } 127 EXPORT_SYMBOL_GPL(nfs_path); 128 129 /* 130 * nfs_d_automount - Handle crossing a mountpoint on the server 131 * @path - The mountpoint 132 * 133 * When we encounter a mountpoint on the server, we want to set up 134 * a mountpoint on the client too, to prevent inode numbers from 135 * colliding, and to allow "df" to work properly. 136 * On NFSv4, we also want to allow for the fact that different 137 * filesystems may be migrated to different servers in a failover 138 * situation, and that different filesystems may want to use 139 * different security flavours. 140 */ 141 struct vfsmount *nfs_d_automount(struct path *path) 142 { 143 struct nfs_fs_context *ctx; 144 struct fs_context *fc; 145 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 146 struct nfs_server *server = NFS_SERVER(d_inode(path->dentry)); 147 struct nfs_client *client = server->nfs_client; 148 int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout); 149 int ret; 150 151 if (IS_ROOT(path->dentry)) 152 return ERR_PTR(-ESTALE); 153 154 /* Open a new filesystem context, transferring parameters from the 155 * parent superblock, including the network namespace. 156 */ 157 fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry); 158 if (IS_ERR(fc)) 159 return ERR_CAST(fc); 160 161 ctx = nfs_fc2context(fc); 162 ctx->clone_data.dentry = path->dentry; 163 ctx->clone_data.sb = path->dentry->d_sb; 164 ctx->clone_data.fattr = nfs_alloc_fattr(); 165 if (!ctx->clone_data.fattr) 166 goto out_fc; 167 168 if (fc->net_ns != client->cl_net) { 169 put_net(fc->net_ns); 170 fc->net_ns = get_net(client->cl_net); 171 } 172 173 /* for submounts we want the same server; referrals will reassign */ 174 memcpy(&ctx->nfs_server.address, &client->cl_addr, client->cl_addrlen); 175 ctx->nfs_server.addrlen = client->cl_addrlen; 176 ctx->nfs_server.port = server->port; 177 178 ctx->version = client->rpc_ops->version; 179 ctx->minorversion = client->cl_minorversion; 180 ctx->nfs_mod = client->cl_nfs_mod; 181 __module_get(ctx->nfs_mod->owner); 182 183 ret = client->rpc_ops->submount(fc, server); 184 if (ret < 0) { 185 mnt = ERR_PTR(ret); 186 goto out_fc; 187 } 188 189 up_write(&fc->root->d_sb->s_umount); 190 mnt = vfs_create_mount(fc); 191 if (IS_ERR(mnt)) 192 goto out_fc; 193 194 mntget(mnt); /* prevent immediate expiration */ 195 if (timeout <= 0) 196 goto out_fc; 197 198 mnt_set_expiry(mnt, &nfs_automount_list); 199 schedule_delayed_work(&nfs_automount_task, timeout); 200 201 out_fc: 202 put_fs_context(fc); 203 return mnt; 204 } 205 206 static int 207 nfs_namespace_getattr(const struct path *path, struct kstat *stat, 208 u32 request_mask, unsigned int query_flags) 209 { 210 if (NFS_FH(d_inode(path->dentry))->size != 0) 211 return nfs_getattr(path, stat, request_mask, query_flags); 212 generic_fillattr(d_inode(path->dentry), stat); 213 return 0; 214 } 215 216 static int 217 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr) 218 { 219 if (NFS_FH(d_inode(dentry))->size != 0) 220 return nfs_setattr(dentry, attr); 221 return -EACCES; 222 } 223 224 const struct inode_operations nfs_mountpoint_inode_operations = { 225 .getattr = nfs_getattr, 226 .setattr = nfs_setattr, 227 }; 228 229 const struct inode_operations nfs_referral_inode_operations = { 230 .getattr = nfs_namespace_getattr, 231 .setattr = nfs_namespace_setattr, 232 }; 233 234 static void nfs_expire_automounts(struct work_struct *work) 235 { 236 struct list_head *list = &nfs_automount_list; 237 int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout); 238 239 mark_mounts_for_expiry(list); 240 if (!list_empty(list) && timeout > 0) 241 schedule_delayed_work(&nfs_automount_task, timeout); 242 } 243 244 void nfs_release_automount_timer(void) 245 { 246 if (list_empty(&nfs_automount_list)) 247 cancel_delayed_work(&nfs_automount_task); 248 } 249 250 /** 251 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 252 * @fc: pointer to struct nfs_fs_context 253 * 254 */ 255 int nfs_do_submount(struct fs_context *fc) 256 { 257 struct nfs_fs_context *ctx = nfs_fc2context(fc); 258 struct dentry *dentry = ctx->clone_data.dentry; 259 struct nfs_server *server; 260 char *buffer, *p; 261 int ret; 262 263 /* create a new volume representation */ 264 server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb), 265 ctx->mntfh, 266 ctx->clone_data.fattr, 267 ctx->selected_flavor); 268 269 if (IS_ERR(server)) 270 return PTR_ERR(server); 271 272 ctx->server = server; 273 274 buffer = kmalloc(4096, GFP_USER); 275 if (!buffer) 276 return -ENOMEM; 277 278 ctx->internal = true; 279 ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits; 280 281 p = nfs_devname(dentry, buffer, 4096); 282 if (IS_ERR(p)) { 283 nfs_errorf(fc, "NFS: Couldn't determine submount pathname"); 284 ret = PTR_ERR(p); 285 } else { 286 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p); 287 if (!ret) 288 ret = vfs_get_tree(fc); 289 } 290 kfree(buffer); 291 return ret; 292 } 293 EXPORT_SYMBOL_GPL(nfs_do_submount); 294 295 int nfs_submount(struct fs_context *fc, struct nfs_server *server) 296 { 297 struct nfs_fs_context *ctx = nfs_fc2context(fc); 298 struct dentry *dentry = ctx->clone_data.dentry; 299 struct dentry *parent = dget_parent(dentry); 300 int err; 301 302 /* Look it up again to get its attributes */ 303 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry, 304 ctx->mntfh, ctx->clone_data.fattr, 305 NULL); 306 dput(parent); 307 if (err != 0) 308 return err; 309 310 ctx->selected_flavor = server->client->cl_auth->au_flavor; 311 return nfs_do_submount(fc); 312 } 313 EXPORT_SYMBOL_GPL(nfs_submount); 314 315 static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp) 316 { 317 long num; 318 int ret; 319 320 if (!val) 321 return -EINVAL; 322 ret = kstrtol(val, 0, &num); 323 if (ret) 324 return -EINVAL; 325 if (num > 0) { 326 if (num >= INT_MAX / HZ) 327 num = INT_MAX; 328 else 329 num *= HZ; 330 *((int *)kp->arg) = num; 331 if (!list_empty(&nfs_automount_list)) 332 mod_delayed_work(system_wq, &nfs_automount_task, num); 333 } else { 334 *((int *)kp->arg) = -1*HZ; 335 cancel_delayed_work(&nfs_automount_task); 336 } 337 return 0; 338 } 339 340 static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp) 341 { 342 long num = *((int *)kp->arg); 343 344 if (num > 0) { 345 if (num >= INT_MAX - (HZ - 1)) 346 num = INT_MAX / HZ; 347 else 348 num = (num + (HZ - 1)) / HZ; 349 } else 350 num = -1; 351 return scnprintf(buffer, PAGE_SIZE, "%li\n", num); 352 } 353 354 static const struct kernel_param_ops param_ops_nfs_timeout = { 355 .set = param_set_nfs_timeout, 356 .get = param_get_nfs_timeout, 357 }; 358 #define param_check_nfs_timeout(name, p) __param_check(name, p, int); 359 360 module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644); 361 MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout, 362 "Set the NFS automounted mountpoint timeout value (seconds)." 363 "Values <= 0 turn expiration off."); 364