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_in - pointer to dentry 36 * @buffer - result buffer 37 * @buflen_in - 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_in, char *buffer, 53 ssize_t buflen_in, unsigned flags) 54 { 55 char *end; 56 int namelen; 57 unsigned seq; 58 const char *base; 59 struct dentry *dentry; 60 ssize_t buflen; 61 62 rename_retry: 63 buflen = buflen_in; 64 dentry = dentry_in; 65 end = buffer+buflen; 66 *--end = '\0'; 67 buflen--; 68 69 seq = read_seqbegin(&rename_lock); 70 rcu_read_lock(); 71 while (1) { 72 spin_lock(&dentry->d_lock); 73 if (IS_ROOT(dentry)) 74 break; 75 namelen = dentry->d_name.len; 76 buflen -= namelen + 1; 77 if (buflen < 0) 78 goto Elong_unlock; 79 end -= namelen; 80 memcpy(end, dentry->d_name.name, namelen); 81 *--end = '/'; 82 spin_unlock(&dentry->d_lock); 83 dentry = dentry->d_parent; 84 } 85 if (read_seqretry(&rename_lock, seq)) { 86 spin_unlock(&dentry->d_lock); 87 rcu_read_unlock(); 88 goto rename_retry; 89 } 90 if ((flags & NFS_PATH_CANONICAL) && *end != '/') { 91 if (--buflen < 0) { 92 spin_unlock(&dentry->d_lock); 93 rcu_read_unlock(); 94 goto Elong; 95 } 96 *--end = '/'; 97 } 98 *p = end; 99 base = dentry->d_fsdata; 100 if (!base) { 101 spin_unlock(&dentry->d_lock); 102 rcu_read_unlock(); 103 WARN_ON(1); 104 return end; 105 } 106 namelen = strlen(base); 107 if (*end == '/') { 108 /* Strip off excess slashes in base string */ 109 while (namelen > 0 && base[namelen - 1] == '/') 110 namelen--; 111 } 112 buflen -= namelen; 113 if (buflen < 0) { 114 spin_unlock(&dentry->d_lock); 115 rcu_read_unlock(); 116 goto Elong; 117 } 118 end -= namelen; 119 memcpy(end, base, namelen); 120 spin_unlock(&dentry->d_lock); 121 rcu_read_unlock(); 122 return end; 123 Elong_unlock: 124 spin_unlock(&dentry->d_lock); 125 rcu_read_unlock(); 126 if (read_seqretry(&rename_lock, seq)) 127 goto rename_retry; 128 Elong: 129 return ERR_PTR(-ENAMETOOLONG); 130 } 131 EXPORT_SYMBOL_GPL(nfs_path); 132 133 /* 134 * nfs_d_automount - Handle crossing a mountpoint on the server 135 * @path - The mountpoint 136 * 137 * When we encounter a mountpoint on the server, we want to set up 138 * a mountpoint on the client too, to prevent inode numbers from 139 * colliding, and to allow "df" to work properly. 140 * On NFSv4, we also want to allow for the fact that different 141 * filesystems may be migrated to different servers in a failover 142 * situation, and that different filesystems may want to use 143 * different security flavours. 144 */ 145 struct vfsmount *nfs_d_automount(struct path *path) 146 { 147 struct nfs_fs_context *ctx; 148 struct fs_context *fc; 149 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 150 struct nfs_server *server = NFS_SB(path->dentry->d_sb); 151 struct nfs_client *client = server->nfs_client; 152 int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout); 153 int ret; 154 155 if (IS_ROOT(path->dentry)) 156 return ERR_PTR(-ESTALE); 157 158 /* Open a new filesystem context, transferring parameters from the 159 * parent superblock, including the network namespace. 160 */ 161 fc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry); 162 if (IS_ERR(fc)) 163 return ERR_CAST(fc); 164 165 ctx = nfs_fc2context(fc); 166 ctx->clone_data.dentry = path->dentry; 167 ctx->clone_data.sb = path->dentry->d_sb; 168 ctx->clone_data.fattr = nfs_alloc_fattr(); 169 if (!ctx->clone_data.fattr) 170 goto out_fc; 171 172 if (fc->net_ns != client->cl_net) { 173 put_net(fc->net_ns); 174 fc->net_ns = get_net(client->cl_net); 175 } 176 177 /* for submounts we want the same server; referrals will reassign */ 178 memcpy(&ctx->nfs_server._address, &client->cl_addr, client->cl_addrlen); 179 ctx->nfs_server.addrlen = client->cl_addrlen; 180 ctx->nfs_server.port = server->port; 181 182 ctx->version = client->rpc_ops->version; 183 ctx->minorversion = client->cl_minorversion; 184 ctx->nfs_mod = client->cl_nfs_mod; 185 __module_get(ctx->nfs_mod->owner); 186 187 ret = client->rpc_ops->submount(fc, server); 188 if (ret < 0) { 189 mnt = ERR_PTR(ret); 190 goto out_fc; 191 } 192 193 up_write(&fc->root->d_sb->s_umount); 194 mnt = vfs_create_mount(fc); 195 if (IS_ERR(mnt)) 196 goto out_fc; 197 198 mntget(mnt); /* prevent immediate expiration */ 199 if (timeout <= 0) 200 goto out_fc; 201 202 mnt_set_expiry(mnt, &nfs_automount_list); 203 schedule_delayed_work(&nfs_automount_task, timeout); 204 205 out_fc: 206 put_fs_context(fc); 207 return mnt; 208 } 209 210 static int 211 nfs_namespace_getattr(struct user_namespace *mnt_userns, 212 const struct path *path, struct kstat *stat, 213 u32 request_mask, unsigned int query_flags) 214 { 215 if (NFS_FH(d_inode(path->dentry))->size != 0) 216 return nfs_getattr(mnt_userns, path, stat, request_mask, 217 query_flags); 218 generic_fillattr(&init_user_ns, d_inode(path->dentry), stat); 219 return 0; 220 } 221 222 static int 223 nfs_namespace_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, 224 struct iattr *attr) 225 { 226 if (NFS_FH(d_inode(dentry))->size != 0) 227 return nfs_setattr(mnt_userns, dentry, attr); 228 return -EACCES; 229 } 230 231 const struct inode_operations nfs_mountpoint_inode_operations = { 232 .getattr = nfs_getattr, 233 .setattr = nfs_setattr, 234 }; 235 236 const struct inode_operations nfs_referral_inode_operations = { 237 .getattr = nfs_namespace_getattr, 238 .setattr = nfs_namespace_setattr, 239 }; 240 241 static void nfs_expire_automounts(struct work_struct *work) 242 { 243 struct list_head *list = &nfs_automount_list; 244 int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout); 245 246 mark_mounts_for_expiry(list); 247 if (!list_empty(list) && timeout > 0) 248 schedule_delayed_work(&nfs_automount_task, timeout); 249 } 250 251 void nfs_release_automount_timer(void) 252 { 253 if (list_empty(&nfs_automount_list)) 254 cancel_delayed_work(&nfs_automount_task); 255 } 256 257 /** 258 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 259 * @fc: pointer to struct nfs_fs_context 260 * 261 */ 262 int nfs_do_submount(struct fs_context *fc) 263 { 264 struct nfs_fs_context *ctx = nfs_fc2context(fc); 265 struct dentry *dentry = ctx->clone_data.dentry; 266 struct nfs_server *server; 267 char *buffer, *p; 268 int ret; 269 270 /* create a new volume representation */ 271 server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb), 272 ctx->mntfh, 273 ctx->clone_data.fattr, 274 ctx->selected_flavor); 275 276 if (IS_ERR(server)) 277 return PTR_ERR(server); 278 279 ctx->server = server; 280 281 buffer = kmalloc(4096, GFP_USER); 282 if (!buffer) 283 return -ENOMEM; 284 285 ctx->internal = true; 286 ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits; 287 288 p = nfs_devname(dentry, buffer, 4096); 289 if (IS_ERR(p)) { 290 nfs_errorf(fc, "NFS: Couldn't determine submount pathname"); 291 ret = PTR_ERR(p); 292 } else { 293 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p); 294 if (!ret) 295 ret = vfs_get_tree(fc); 296 } 297 kfree(buffer); 298 return ret; 299 } 300 EXPORT_SYMBOL_GPL(nfs_do_submount); 301 302 int nfs_submount(struct fs_context *fc, struct nfs_server *server) 303 { 304 struct nfs_fs_context *ctx = nfs_fc2context(fc); 305 struct dentry *dentry = ctx->clone_data.dentry; 306 struct dentry *parent = dget_parent(dentry); 307 int err; 308 309 /* Look it up again to get its attributes */ 310 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry, 311 ctx->mntfh, ctx->clone_data.fattr); 312 dput(parent); 313 if (err != 0) 314 return err; 315 316 ctx->selected_flavor = server->client->cl_auth->au_flavor; 317 return nfs_do_submount(fc); 318 } 319 EXPORT_SYMBOL_GPL(nfs_submount); 320 321 static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp) 322 { 323 long num; 324 int ret; 325 326 if (!val) 327 return -EINVAL; 328 ret = kstrtol(val, 0, &num); 329 if (ret) 330 return -EINVAL; 331 if (num > 0) { 332 if (num >= INT_MAX / HZ) 333 num = INT_MAX; 334 else 335 num *= HZ; 336 *((int *)kp->arg) = num; 337 if (!list_empty(&nfs_automount_list)) 338 mod_delayed_work(system_wq, &nfs_automount_task, num); 339 } else { 340 *((int *)kp->arg) = -1*HZ; 341 cancel_delayed_work(&nfs_automount_task); 342 } 343 return 0; 344 } 345 346 static int param_get_nfs_timeout(char *buffer, const struct kernel_param *kp) 347 { 348 long num = *((int *)kp->arg); 349 350 if (num > 0) { 351 if (num >= INT_MAX - (HZ - 1)) 352 num = INT_MAX / HZ; 353 else 354 num = (num + (HZ - 1)) / HZ; 355 } else 356 num = -1; 357 return sysfs_emit(buffer, "%li\n", num); 358 } 359 360 static const struct kernel_param_ops param_ops_nfs_timeout = { 361 .set = param_set_nfs_timeout, 362 .get = param_get_nfs_timeout, 363 }; 364 #define param_check_nfs_timeout(name, p) __param_check(name, p, int) 365 366 module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644); 367 MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout, 368 "Set the NFS automounted mountpoint timeout value (seconds)." 369 "Values <= 0 turn expiration off."); 370