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 ret; 149 150 if (IS_ROOT(path->dentry)) 151 return ERR_PTR(-ESTALE); 152 153 /* Open a new filesystem context, transferring parameters from the 154 * parent superblock, including the network namespace. 155 */ 156 fc = fs_context_for_submount(&nfs_fs_type, path->dentry); 157 if (IS_ERR(fc)) 158 return ERR_CAST(fc); 159 160 ctx = nfs_fc2context(fc); 161 ctx->clone_data.dentry = path->dentry; 162 ctx->clone_data.sb = path->dentry->d_sb; 163 ctx->clone_data.fattr = nfs_alloc_fattr(); 164 if (!ctx->clone_data.fattr) 165 goto out_fc; 166 167 if (fc->net_ns != client->cl_net) { 168 put_net(fc->net_ns); 169 fc->net_ns = get_net(client->cl_net); 170 } 171 172 /* for submounts we want the same server; referrals will reassign */ 173 memcpy(&ctx->nfs_server.address, &client->cl_addr, client->cl_addrlen); 174 ctx->nfs_server.addrlen = client->cl_addrlen; 175 ctx->nfs_server.port = server->port; 176 177 ctx->version = client->rpc_ops->version; 178 ctx->minorversion = client->cl_minorversion; 179 ctx->nfs_mod = client->cl_nfs_mod; 180 __module_get(ctx->nfs_mod->owner); 181 182 ret = client->rpc_ops->submount(fc, server); 183 if (ret < 0) { 184 mnt = ERR_PTR(ret); 185 goto out_fc; 186 } 187 188 up_write(&fc->root->d_sb->s_umount); 189 mnt = vfs_create_mount(fc); 190 if (IS_ERR(mnt)) 191 goto out_fc; 192 193 if (nfs_mountpoint_expiry_timeout < 0) 194 goto out_fc; 195 196 mntget(mnt); /* prevent immediate expiration */ 197 mnt_set_expiry(mnt, &nfs_automount_list); 198 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 199 200 out_fc: 201 put_fs_context(fc); 202 return mnt; 203 } 204 205 static int 206 nfs_namespace_getattr(const struct path *path, struct kstat *stat, 207 u32 request_mask, unsigned int query_flags) 208 { 209 if (NFS_FH(d_inode(path->dentry))->size != 0) 210 return nfs_getattr(path, stat, request_mask, query_flags); 211 generic_fillattr(d_inode(path->dentry), stat); 212 return 0; 213 } 214 215 static int 216 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr) 217 { 218 if (NFS_FH(d_inode(dentry))->size != 0) 219 return nfs_setattr(dentry, attr); 220 return -EACCES; 221 } 222 223 const struct inode_operations nfs_mountpoint_inode_operations = { 224 .getattr = nfs_getattr, 225 .setattr = nfs_setattr, 226 }; 227 228 const struct inode_operations nfs_referral_inode_operations = { 229 .getattr = nfs_namespace_getattr, 230 .setattr = nfs_namespace_setattr, 231 }; 232 233 static void nfs_expire_automounts(struct work_struct *work) 234 { 235 struct list_head *list = &nfs_automount_list; 236 237 mark_mounts_for_expiry(list); 238 if (!list_empty(list)) 239 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 240 } 241 242 void nfs_release_automount_timer(void) 243 { 244 if (list_empty(&nfs_automount_list)) 245 cancel_delayed_work(&nfs_automount_task); 246 } 247 248 /** 249 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 250 * @dentry: parent directory 251 * @fh: filehandle for new root dentry 252 * @fattr: attributes for new root inode 253 * @authflavor: security flavor to use when performing the mount 254 * 255 */ 256 int nfs_do_submount(struct fs_context *fc) 257 { 258 struct nfs_fs_context *ctx = nfs_fc2context(fc); 259 struct dentry *dentry = ctx->clone_data.dentry; 260 struct nfs_server *server; 261 char *buffer, *p; 262 int ret; 263 264 /* create a new volume representation */ 265 server = ctx->nfs_mod->rpc_ops->clone_server(NFS_SB(ctx->clone_data.sb), 266 ctx->mntfh, 267 ctx->clone_data.fattr, 268 ctx->selected_flavor); 269 270 if (IS_ERR(server)) 271 return PTR_ERR(server); 272 273 ctx->server = server; 274 275 buffer = kmalloc(4096, GFP_USER); 276 if (!buffer) 277 return -ENOMEM; 278 279 ctx->internal = true; 280 ctx->clone_data.inherited_bsize = ctx->clone_data.sb->s_blocksize_bits; 281 282 p = nfs_devname(dentry, buffer, 4096); 283 if (IS_ERR(p)) { 284 nfs_errorf(fc, "NFS: Couldn't determine submount pathname"); 285 ret = PTR_ERR(p); 286 } else { 287 ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p); 288 if (!ret) 289 ret = vfs_get_tree(fc); 290 } 291 kfree(buffer); 292 return ret; 293 } 294 EXPORT_SYMBOL_GPL(nfs_do_submount); 295 296 int nfs_submount(struct fs_context *fc, struct nfs_server *server) 297 { 298 struct nfs_fs_context *ctx = nfs_fc2context(fc); 299 struct dentry *dentry = ctx->clone_data.dentry; 300 struct dentry *parent = dget_parent(dentry); 301 int err; 302 303 /* Look it up again to get its attributes */ 304 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), dentry, 305 ctx->mntfh, ctx->clone_data.fattr, 306 NULL); 307 dput(parent); 308 if (err != 0) 309 return err; 310 311 ctx->selected_flavor = server->client->cl_auth->au_flavor; 312 return nfs_do_submount(fc); 313 } 314 EXPORT_SYMBOL_GPL(nfs_submount); 315