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TOMOYO Linux Cross Reference
Linux/fs/hostfs/hostfs_kern.c

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  1 /*
  2  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  3  * Licensed under the GPL
  4  *
  5  * Ported the filesystem routines to 2.5.
  6  * 2003-02-10 Petr Baudis <pasky@ucw.cz>
  7  */
  8 
  9 #include <linux/fs.h>
 10 #include <linux/magic.h>
 11 #include <linux/module.h>
 12 #include <linux/mm.h>
 13 #include <linux/pagemap.h>
 14 #include <linux/statfs.h>
 15 #include <linux/slab.h>
 16 #include <linux/seq_file.h>
 17 #include <linux/mount.h>
 18 #include <linux/namei.h>
 19 #include "hostfs.h"
 20 #include <init.h>
 21 #include <kern.h>
 22 
 23 struct hostfs_inode_info {
 24         int fd;
 25         fmode_t mode;
 26         struct inode vfs_inode;
 27         struct mutex open_mutex;
 28 };
 29 
 30 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
 31 {
 32         return list_entry(inode, struct hostfs_inode_info, vfs_inode);
 33 }
 34 
 35 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
 36 
 37 static struct kmem_cache *hostfs_inode_cache;
 38 
 39 /* Changed in hostfs_args before the kernel starts running */
 40 static char *root_ino = "";
 41 static int append = 0;
 42 
 43 static const struct inode_operations hostfs_iops;
 44 static const struct inode_operations hostfs_dir_iops;
 45 static const struct inode_operations hostfs_link_iops;
 46 
 47 #ifndef MODULE
 48 static int __init hostfs_args(char *options, int *add)
 49 {
 50         char *ptr;
 51 
 52         ptr = strchr(options, ',');
 53         if (ptr != NULL)
 54                 *ptr++ = '\0';
 55         if (*options != '\0')
 56                 root_ino = options;
 57 
 58         options = ptr;
 59         while (options) {
 60                 ptr = strchr(options, ',');
 61                 if (ptr != NULL)
 62                         *ptr++ = '\0';
 63                 if (*options != '\0') {
 64                         if (!strcmp(options, "append"))
 65                                 append = 1;
 66                         else printf("hostfs_args - unsupported option - %s\n",
 67                                     options);
 68                 }
 69                 options = ptr;
 70         }
 71         return 0;
 72 }
 73 
 74 __uml_setup("hostfs=", hostfs_args,
 75 "hostfs=<root dir>,<flags>,...\n"
 76 "    This is used to set hostfs parameters.  The root directory argument\n"
 77 "    is used to confine all hostfs mounts to within the specified directory\n"
 78 "    tree on the host.  If this isn't specified, then a user inside UML can\n"
 79 "    mount anything on the host that's accessible to the user that's running\n"
 80 "    it.\n"
 81 "    The only flag currently supported is 'append', which specifies that all\n"
 82 "    files opened by hostfs will be opened in append mode.\n\n"
 83 );
 84 #endif
 85 
 86 static char *__dentry_name(struct dentry *dentry, char *name)
 87 {
 88         char *p = dentry_path_raw(dentry, name, PATH_MAX);
 89         char *root;
 90         size_t len;
 91 
 92         root = dentry->d_sb->s_fs_info;
 93         len = strlen(root);
 94         if (IS_ERR(p)) {
 95                 __putname(name);
 96                 return NULL;
 97         }
 98 
 99         /*
100          * This function relies on the fact that dentry_path_raw() will place
101          * the path name at the end of the provided buffer.
102          */
103         BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);
104 
105         strlcpy(name, root, PATH_MAX);
106         if (len > p - name) {
107                 __putname(name);
108                 return NULL;
109         }
110 
111         if (p > name + len)
112                 strcpy(name + len, p);
113 
114         return name;
115 }
116 
117 static char *dentry_name(struct dentry *dentry)
118 {
119         char *name = __getname();
120         if (!name)
121                 return NULL;
122 
123         return __dentry_name(dentry, name);
124 }
125 
126 static char *inode_name(struct inode *ino)
127 {
128         struct dentry *dentry;
129         char *name;
130 
131         dentry = d_find_alias(ino);
132         if (!dentry)
133                 return NULL;
134 
135         name = dentry_name(dentry);
136 
137         dput(dentry);
138 
139         return name;
140 }
141 
142 static char *follow_link(char *link)
143 {
144         char *name, *resolved, *end;
145         int n;
146 
147         name = kmalloc(PATH_MAX, GFP_KERNEL);
148         if (!name) {
149                 n = -ENOMEM;
150                 goto out_free;
151         }
152 
153         n = hostfs_do_readlink(link, name, PATH_MAX);
154         if (n < 0)
155                 goto out_free;
156         else if (n == PATH_MAX) {
157                 n = -E2BIG;
158                 goto out_free;
159         }
160 
161         if (*name == '/')
162                 return name;
163 
164         end = strrchr(link, '/');
165         if (end == NULL)
166                 return name;
167 
168         *(end + 1) = '\0';
169 
170         resolved = kasprintf(GFP_KERNEL, "%s%s", link, name);
171         if (resolved == NULL) {
172                 n = -ENOMEM;
173                 goto out_free;
174         }
175 
176         kfree(name);
177         return resolved;
178 
179  out_free:
180         kfree(name);
181         return ERR_PTR(n);
182 }
183 
184 static struct inode *hostfs_iget(struct super_block *sb)
185 {
186         struct inode *inode = new_inode(sb);
187         if (!inode)
188                 return ERR_PTR(-ENOMEM);
189         return inode;
190 }
191 
192 static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
193 {
194         /*
195          * do_statfs uses struct statfs64 internally, but the linux kernel
196          * struct statfs still has 32-bit versions for most of these fields,
197          * so we convert them here
198          */
199         int err;
200         long long f_blocks;
201         long long f_bfree;
202         long long f_bavail;
203         long long f_files;
204         long long f_ffree;
205 
206         err = do_statfs(dentry->d_sb->s_fs_info,
207                         &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
208                         &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
209                         &sf->f_namelen);
210         if (err)
211                 return err;
212         sf->f_blocks = f_blocks;
213         sf->f_bfree = f_bfree;
214         sf->f_bavail = f_bavail;
215         sf->f_files = f_files;
216         sf->f_ffree = f_ffree;
217         sf->f_type = HOSTFS_SUPER_MAGIC;
218         return 0;
219 }
220 
221 static struct inode *hostfs_alloc_inode(struct super_block *sb)
222 {
223         struct hostfs_inode_info *hi;
224 
225         hi = kmem_cache_alloc(hostfs_inode_cache, GFP_KERNEL_ACCOUNT);
226         if (hi == NULL)
227                 return NULL;
228         hi->fd = -1;
229         hi->mode = 0;
230         inode_init_once(&hi->vfs_inode);
231         mutex_init(&hi->open_mutex);
232         return &hi->vfs_inode;
233 }
234 
235 static void hostfs_evict_inode(struct inode *inode)
236 {
237         truncate_inode_pages_final(&inode->i_data);
238         clear_inode(inode);
239         if (HOSTFS_I(inode)->fd != -1) {
240                 close_file(&HOSTFS_I(inode)->fd);
241                 HOSTFS_I(inode)->fd = -1;
242         }
243 }
244 
245 static void hostfs_free_inode(struct inode *inode)
246 {
247         kmem_cache_free(hostfs_inode_cache, HOSTFS_I(inode));
248 }
249 
250 static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
251 {
252         const char *root_path = root->d_sb->s_fs_info;
253         size_t offset = strlen(root_ino) + 1;
254 
255         if (strlen(root_path) > offset)
256                 seq_show_option(seq, root_path + offset, NULL);
257 
258         if (append)
259                 seq_puts(seq, ",append");
260 
261         return 0;
262 }
263 
264 static const struct super_operations hostfs_sbops = {
265         .alloc_inode    = hostfs_alloc_inode,
266         .free_inode     = hostfs_free_inode,
267         .evict_inode    = hostfs_evict_inode,
268         .statfs         = hostfs_statfs,
269         .show_options   = hostfs_show_options,
270 };
271 
272 static int hostfs_readdir(struct file *file, struct dir_context *ctx)
273 {
274         void *dir;
275         char *name;
276         unsigned long long next, ino;
277         int error, len;
278         unsigned int type;
279 
280         name = dentry_name(file->f_path.dentry);
281         if (name == NULL)
282                 return -ENOMEM;
283         dir = open_dir(name, &error);
284         __putname(name);
285         if (dir == NULL)
286                 return -error;
287         next = ctx->pos;
288         seek_dir(dir, next);
289         while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
290                 if (!dir_emit(ctx, name, len, ino, type))
291                         break;
292                 ctx->pos = next;
293         }
294         close_dir(dir);
295         return 0;
296 }
297 
298 static int hostfs_open(struct inode *ino, struct file *file)
299 {
300         char *name;
301         fmode_t mode;
302         int err;
303         int r, w, fd;
304 
305         mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
306         if ((mode & HOSTFS_I(ino)->mode) == mode)
307                 return 0;
308 
309         mode |= HOSTFS_I(ino)->mode;
310 
311 retry:
312         r = w = 0;
313 
314         if (mode & FMODE_READ)
315                 r = 1;
316         if (mode & FMODE_WRITE)
317                 r = w = 1;
318 
319         name = dentry_name(file_dentry(file));
320         if (name == NULL)
321                 return -ENOMEM;
322 
323         fd = open_file(name, r, w, append);
324         __putname(name);
325         if (fd < 0)
326                 return fd;
327 
328         mutex_lock(&HOSTFS_I(ino)->open_mutex);
329         /* somebody else had handled it first? */
330         if ((mode & HOSTFS_I(ino)->mode) == mode) {
331                 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
332                 close_file(&fd);
333                 return 0;
334         }
335         if ((mode | HOSTFS_I(ino)->mode) != mode) {
336                 mode |= HOSTFS_I(ino)->mode;
337                 mutex_unlock(&HOSTFS_I(ino)->open_mutex);
338                 close_file(&fd);
339                 goto retry;
340         }
341         if (HOSTFS_I(ino)->fd == -1) {
342                 HOSTFS_I(ino)->fd = fd;
343         } else {
344                 err = replace_file(fd, HOSTFS_I(ino)->fd);
345                 close_file(&fd);
346                 if (err < 0) {
347                         mutex_unlock(&HOSTFS_I(ino)->open_mutex);
348                         return err;
349                 }
350         }
351         HOSTFS_I(ino)->mode = mode;
352         mutex_unlock(&HOSTFS_I(ino)->open_mutex);
353 
354         return 0;
355 }
356 
357 static int hostfs_file_release(struct inode *inode, struct file *file)
358 {
359         filemap_write_and_wait(inode->i_mapping);
360 
361         return 0;
362 }
363 
364 static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
365                         int datasync)
366 {
367         struct inode *inode = file->f_mapping->host;
368         int ret;
369 
370         ret = file_write_and_wait_range(file, start, end);
371         if (ret)
372                 return ret;
373 
374         inode_lock(inode);
375         ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
376         inode_unlock(inode);
377 
378         return ret;
379 }
380 
381 static const struct file_operations hostfs_file_fops = {
382         .llseek         = generic_file_llseek,
383         .splice_read    = generic_file_splice_read,
384         .read_iter      = generic_file_read_iter,
385         .write_iter     = generic_file_write_iter,
386         .mmap           = generic_file_mmap,
387         .open           = hostfs_open,
388         .release        = hostfs_file_release,
389         .fsync          = hostfs_fsync,
390 };
391 
392 static const struct file_operations hostfs_dir_fops = {
393         .llseek         = generic_file_llseek,
394         .iterate_shared = hostfs_readdir,
395         .read           = generic_read_dir,
396         .open           = hostfs_open,
397         .fsync          = hostfs_fsync,
398 };
399 
400 static int hostfs_writepage(struct page *page, struct writeback_control *wbc)
401 {
402         struct address_space *mapping = page->mapping;
403         struct inode *inode = mapping->host;
404         char *buffer;
405         loff_t base = page_offset(page);
406         int count = PAGE_SIZE;
407         int end_index = inode->i_size >> PAGE_SHIFT;
408         int err;
409 
410         if (page->index >= end_index)
411                 count = inode->i_size & (PAGE_SIZE-1);
412 
413         buffer = kmap(page);
414 
415         err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count);
416         if (err != count) {
417                 ClearPageUptodate(page);
418                 goto out;
419         }
420 
421         if (base > inode->i_size)
422                 inode->i_size = base;
423 
424         if (PageError(page))
425                 ClearPageError(page);
426         err = 0;
427 
428  out:
429         kunmap(page);
430 
431         unlock_page(page);
432         return err;
433 }
434 
435 static int hostfs_readpage(struct file *file, struct page *page)
436 {
437         char *buffer;
438         loff_t start = page_offset(page);
439         int bytes_read, ret = 0;
440 
441         buffer = kmap(page);
442         bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
443                         PAGE_SIZE);
444         if (bytes_read < 0) {
445                 ClearPageUptodate(page);
446                 SetPageError(page);
447                 ret = bytes_read;
448                 goto out;
449         }
450 
451         memset(buffer + bytes_read, 0, PAGE_SIZE - bytes_read);
452 
453         ClearPageError(page);
454         SetPageUptodate(page);
455 
456  out:
457         flush_dcache_page(page);
458         kunmap(page);
459         unlock_page(page);
460         return ret;
461 }
462 
463 static int hostfs_write_begin(struct file *file, struct address_space *mapping,
464                               loff_t pos, unsigned len, unsigned flags,
465                               struct page **pagep, void **fsdata)
466 {
467         pgoff_t index = pos >> PAGE_SHIFT;
468 
469         *pagep = grab_cache_page_write_begin(mapping, index, flags);
470         if (!*pagep)
471                 return -ENOMEM;
472         return 0;
473 }
474 
475 static int hostfs_write_end(struct file *file, struct address_space *mapping,
476                             loff_t pos, unsigned len, unsigned copied,
477                             struct page *page, void *fsdata)
478 {
479         struct inode *inode = mapping->host;
480         void *buffer;
481         unsigned from = pos & (PAGE_SIZE - 1);
482         int err;
483 
484         buffer = kmap(page);
485         err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer + from, copied);
486         kunmap(page);
487 
488         if (!PageUptodate(page) && err == PAGE_SIZE)
489                 SetPageUptodate(page);
490 
491         /*
492          * If err > 0, write_file has added err to pos, so we are comparing
493          * i_size against the last byte written.
494          */
495         if (err > 0 && (pos > inode->i_size))
496                 inode->i_size = pos;
497         unlock_page(page);
498         put_page(page);
499 
500         return err;
501 }
502 
503 static const struct address_space_operations hostfs_aops = {
504         .writepage      = hostfs_writepage,
505         .readpage       = hostfs_readpage,
506         .set_page_dirty = __set_page_dirty_nobuffers,
507         .write_begin    = hostfs_write_begin,
508         .write_end      = hostfs_write_end,
509 };
510 
511 static int read_name(struct inode *ino, char *name)
512 {
513         dev_t rdev;
514         struct hostfs_stat st;
515         int err = stat_file(name, &st, -1);
516         if (err)
517                 return err;
518 
519         /* Reencode maj and min with the kernel encoding.*/
520         rdev = MKDEV(st.maj, st.min);
521 
522         switch (st.mode & S_IFMT) {
523         case S_IFLNK:
524                 ino->i_op = &hostfs_link_iops;
525                 break;
526         case S_IFDIR:
527                 ino->i_op = &hostfs_dir_iops;
528                 ino->i_fop = &hostfs_dir_fops;
529                 break;
530         case S_IFCHR:
531         case S_IFBLK:
532         case S_IFIFO:
533         case S_IFSOCK:
534                 init_special_inode(ino, st.mode & S_IFMT, rdev);
535                 ino->i_op = &hostfs_iops;
536                 break;
537         case S_IFREG:
538                 ino->i_op = &hostfs_iops;
539                 ino->i_fop = &hostfs_file_fops;
540                 ino->i_mapping->a_ops = &hostfs_aops;
541                 break;
542         default:
543                 return -EIO;
544         }
545 
546         ino->i_ino = st.ino;
547         ino->i_mode = st.mode;
548         set_nlink(ino, st.nlink);
549         i_uid_write(ino, st.uid);
550         i_gid_write(ino, st.gid);
551         ino->i_atime = (struct timespec64){ st.atime.tv_sec, st.atime.tv_nsec };
552         ino->i_mtime = (struct timespec64){ st.mtime.tv_sec, st.mtime.tv_nsec };
553         ino->i_ctime = (struct timespec64){ st.ctime.tv_sec, st.ctime.tv_nsec };
554         ino->i_size = st.size;
555         ino->i_blocks = st.blocks;
556         return 0;
557 }
558 
559 static int hostfs_create(struct user_namespace *mnt_userns, struct inode *dir,
560                          struct dentry *dentry, umode_t mode, bool excl)
561 {
562         struct inode *inode;
563         char *name;
564         int error, fd;
565 
566         inode = hostfs_iget(dir->i_sb);
567         if (IS_ERR(inode)) {
568                 error = PTR_ERR(inode);
569                 goto out;
570         }
571 
572         error = -ENOMEM;
573         name = dentry_name(dentry);
574         if (name == NULL)
575                 goto out_put;
576 
577         fd = file_create(name, mode & 0777);
578         if (fd < 0)
579                 error = fd;
580         else
581                 error = read_name(inode, name);
582 
583         __putname(name);
584         if (error)
585                 goto out_put;
586 
587         HOSTFS_I(inode)->fd = fd;
588         HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
589         d_instantiate(dentry, inode);
590         return 0;
591 
592  out_put:
593         iput(inode);
594  out:
595         return error;
596 }
597 
598 static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
599                                     unsigned int flags)
600 {
601         struct inode *inode;
602         char *name;
603         int err;
604 
605         inode = hostfs_iget(ino->i_sb);
606         if (IS_ERR(inode))
607                 goto out;
608 
609         err = -ENOMEM;
610         name = dentry_name(dentry);
611         if (name) {
612                 err = read_name(inode, name);
613                 __putname(name);
614         }
615         if (err) {
616                 iput(inode);
617                 inode = (err == -ENOENT) ? NULL : ERR_PTR(err);
618         }
619  out:
620         return d_splice_alias(inode, dentry);
621 }
622 
623 static int hostfs_link(struct dentry *to, struct inode *ino,
624                        struct dentry *from)
625 {
626         char *from_name, *to_name;
627         int err;
628 
629         if ((from_name = dentry_name(from)) == NULL)
630                 return -ENOMEM;
631         to_name = dentry_name(to);
632         if (to_name == NULL) {
633                 __putname(from_name);
634                 return -ENOMEM;
635         }
636         err = link_file(to_name, from_name);
637         __putname(from_name);
638         __putname(to_name);
639         return err;
640 }
641 
642 static int hostfs_unlink(struct inode *ino, struct dentry *dentry)
643 {
644         char *file;
645         int err;
646 
647         if (append)
648                 return -EPERM;
649 
650         if ((file = dentry_name(dentry)) == NULL)
651                 return -ENOMEM;
652 
653         err = unlink_file(file);
654         __putname(file);
655         return err;
656 }
657 
658 static int hostfs_symlink(struct user_namespace *mnt_userns, struct inode *ino,
659                           struct dentry *dentry, const char *to)
660 {
661         char *file;
662         int err;
663 
664         if ((file = dentry_name(dentry)) == NULL)
665                 return -ENOMEM;
666         err = make_symlink(file, to);
667         __putname(file);
668         return err;
669 }
670 
671 static int hostfs_mkdir(struct user_namespace *mnt_userns, struct inode *ino,
672                         struct dentry *dentry, umode_t mode)
673 {
674         char *file;
675         int err;
676 
677         if ((file = dentry_name(dentry)) == NULL)
678                 return -ENOMEM;
679         err = do_mkdir(file, mode);
680         __putname(file);
681         return err;
682 }
683 
684 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
685 {
686         char *file;
687         int err;
688 
689         if ((file = dentry_name(dentry)) == NULL)
690                 return -ENOMEM;
691         err = hostfs_do_rmdir(file);
692         __putname(file);
693         return err;
694 }
695 
696 static int hostfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
697                         struct dentry *dentry, umode_t mode, dev_t dev)
698 {
699         struct inode *inode;
700         char *name;
701         int err;
702 
703         inode = hostfs_iget(dir->i_sb);
704         if (IS_ERR(inode)) {
705                 err = PTR_ERR(inode);
706                 goto out;
707         }
708 
709         err = -ENOMEM;
710         name = dentry_name(dentry);
711         if (name == NULL)
712                 goto out_put;
713 
714         err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
715         if (err)
716                 goto out_free;
717 
718         err = read_name(inode, name);
719         __putname(name);
720         if (err)
721                 goto out_put;
722 
723         d_instantiate(dentry, inode);
724         return 0;
725 
726  out_free:
727         __putname(name);
728  out_put:
729         iput(inode);
730  out:
731         return err;
732 }
733 
734 static int hostfs_rename2(struct user_namespace *mnt_userns,
735                           struct inode *old_dir, struct dentry *old_dentry,
736                           struct inode *new_dir, struct dentry *new_dentry,
737                           unsigned int flags)
738 {
739         char *old_name, *new_name;
740         int err;
741 
742         if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
743                 return -EINVAL;
744 
745         old_name = dentry_name(old_dentry);
746         if (old_name == NULL)
747                 return -ENOMEM;
748         new_name = dentry_name(new_dentry);
749         if (new_name == NULL) {
750                 __putname(old_name);
751                 return -ENOMEM;
752         }
753         if (!flags)
754                 err = rename_file(old_name, new_name);
755         else
756                 err = rename2_file(old_name, new_name, flags);
757 
758         __putname(old_name);
759         __putname(new_name);
760         return err;
761 }
762 
763 static int hostfs_permission(struct user_namespace *mnt_userns,
764                              struct inode *ino, int desired)
765 {
766         char *name;
767         int r = 0, w = 0, x = 0, err;
768 
769         if (desired & MAY_NOT_BLOCK)
770                 return -ECHILD;
771 
772         if (desired & MAY_READ) r = 1;
773         if (desired & MAY_WRITE) w = 1;
774         if (desired & MAY_EXEC) x = 1;
775         name = inode_name(ino);
776         if (name == NULL)
777                 return -ENOMEM;
778 
779         if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
780             S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
781                 err = 0;
782         else
783                 err = access_file(name, r, w, x);
784         __putname(name);
785         if (!err)
786                 err = generic_permission(&init_user_ns, ino, desired);
787         return err;
788 }
789 
790 static int hostfs_setattr(struct user_namespace *mnt_userns,
791                           struct dentry *dentry, struct iattr *attr)
792 {
793         struct inode *inode = d_inode(dentry);
794         struct hostfs_iattr attrs;
795         char *name;
796         int err;
797 
798         int fd = HOSTFS_I(inode)->fd;
799 
800         err = setattr_prepare(&init_user_ns, dentry, attr);
801         if (err)
802                 return err;
803 
804         if (append)
805                 attr->ia_valid &= ~ATTR_SIZE;
806 
807         attrs.ia_valid = 0;
808         if (attr->ia_valid & ATTR_MODE) {
809                 attrs.ia_valid |= HOSTFS_ATTR_MODE;
810                 attrs.ia_mode = attr->ia_mode;
811         }
812         if (attr->ia_valid & ATTR_UID) {
813                 attrs.ia_valid |= HOSTFS_ATTR_UID;
814                 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
815         }
816         if (attr->ia_valid & ATTR_GID) {
817                 attrs.ia_valid |= HOSTFS_ATTR_GID;
818                 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
819         }
820         if (attr->ia_valid & ATTR_SIZE) {
821                 attrs.ia_valid |= HOSTFS_ATTR_SIZE;
822                 attrs.ia_size = attr->ia_size;
823         }
824         if (attr->ia_valid & ATTR_ATIME) {
825                 attrs.ia_valid |= HOSTFS_ATTR_ATIME;
826                 attrs.ia_atime = (struct hostfs_timespec)
827                         { attr->ia_atime.tv_sec, attr->ia_atime.tv_nsec };
828         }
829         if (attr->ia_valid & ATTR_MTIME) {
830                 attrs.ia_valid |= HOSTFS_ATTR_MTIME;
831                 attrs.ia_mtime = (struct hostfs_timespec)
832                         { attr->ia_mtime.tv_sec, attr->ia_mtime.tv_nsec };
833         }
834         if (attr->ia_valid & ATTR_CTIME) {
835                 attrs.ia_valid |= HOSTFS_ATTR_CTIME;
836                 attrs.ia_ctime = (struct hostfs_timespec)
837                         { attr->ia_ctime.tv_sec, attr->ia_ctime.tv_nsec };
838         }
839         if (attr->ia_valid & ATTR_ATIME_SET) {
840                 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
841         }
842         if (attr->ia_valid & ATTR_MTIME_SET) {
843                 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
844         }
845         name = dentry_name(dentry);
846         if (name == NULL)
847                 return -ENOMEM;
848         err = set_attr(name, &attrs, fd);
849         __putname(name);
850         if (err)
851                 return err;
852 
853         if ((attr->ia_valid & ATTR_SIZE) &&
854             attr->ia_size != i_size_read(inode))
855                 truncate_setsize(inode, attr->ia_size);
856 
857         setattr_copy(&init_user_ns, inode, attr);
858         mark_inode_dirty(inode);
859         return 0;
860 }
861 
862 static const struct inode_operations hostfs_iops = {
863         .permission     = hostfs_permission,
864         .setattr        = hostfs_setattr,
865 };
866 
867 static const struct inode_operations hostfs_dir_iops = {
868         .create         = hostfs_create,
869         .lookup         = hostfs_lookup,
870         .link           = hostfs_link,
871         .unlink         = hostfs_unlink,
872         .symlink        = hostfs_symlink,
873         .mkdir          = hostfs_mkdir,
874         .rmdir          = hostfs_rmdir,
875         .mknod          = hostfs_mknod,
876         .rename         = hostfs_rename2,
877         .permission     = hostfs_permission,
878         .setattr        = hostfs_setattr,
879 };
880 
881 static const char *hostfs_get_link(struct dentry *dentry,
882                                    struct inode *inode,
883                                    struct delayed_call *done)
884 {
885         char *link;
886         if (!dentry)
887                 return ERR_PTR(-ECHILD);
888         link = kmalloc(PATH_MAX, GFP_KERNEL);
889         if (link) {
890                 char *path = dentry_name(dentry);
891                 int err = -ENOMEM;
892                 if (path) {
893                         err = hostfs_do_readlink(path, link, PATH_MAX);
894                         if (err == PATH_MAX)
895                                 err = -E2BIG;
896                         __putname(path);
897                 }
898                 if (err < 0) {
899                         kfree(link);
900                         return ERR_PTR(err);
901                 }
902         } else {
903                 return ERR_PTR(-ENOMEM);
904         }
905 
906         set_delayed_call(done, kfree_link, link);
907         return link;
908 }
909 
910 static const struct inode_operations hostfs_link_iops = {
911         .get_link       = hostfs_get_link,
912 };
913 
914 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)
915 {
916         struct inode *root_inode;
917         char *host_root_path, *req_root = d;
918         int err;
919 
920         sb->s_blocksize = 1024;
921         sb->s_blocksize_bits = 10;
922         sb->s_magic = HOSTFS_SUPER_MAGIC;
923         sb->s_op = &hostfs_sbops;
924         sb->s_d_op = &simple_dentry_operations;
925         sb->s_maxbytes = MAX_LFS_FILESIZE;
926 
927         /* NULL is printed as '(null)' by printf(): avoid that. */
928         if (req_root == NULL)
929                 req_root = "";
930 
931         err = -ENOMEM;
932         sb->s_fs_info = host_root_path =
933                 kasprintf(GFP_KERNEL, "%s/%s", root_ino, req_root);
934         if (host_root_path == NULL)
935                 goto out;
936 
937         root_inode = new_inode(sb);
938         if (!root_inode)
939                 goto out;
940 
941         err = read_name(root_inode, host_root_path);
942         if (err)
943                 goto out_put;
944 
945         if (S_ISLNK(root_inode->i_mode)) {
946                 char *name = follow_link(host_root_path);
947                 if (IS_ERR(name)) {
948                         err = PTR_ERR(name);
949                         goto out_put;
950                 }
951                 err = read_name(root_inode, name);
952                 kfree(name);
953                 if (err)
954                         goto out_put;
955         }
956 
957         err = -ENOMEM;
958         sb->s_root = d_make_root(root_inode);
959         if (sb->s_root == NULL)
960                 goto out;
961 
962         return 0;
963 
964 out_put:
965         iput(root_inode);
966 out:
967         return err;
968 }
969 
970 static struct dentry *hostfs_read_sb(struct file_system_type *type,
971                           int flags, const char *dev_name,
972                           void *data)
973 {
974         return mount_nodev(type, flags, data, hostfs_fill_sb_common);
975 }
976 
977 static void hostfs_kill_sb(struct super_block *s)
978 {
979         kill_anon_super(s);
980         kfree(s->s_fs_info);
981 }
982 
983 static struct file_system_type hostfs_type = {
984         .owner          = THIS_MODULE,
985         .name           = "hostfs",
986         .mount          = hostfs_read_sb,
987         .kill_sb        = hostfs_kill_sb,
988         .fs_flags       = 0,
989 };
990 MODULE_ALIAS_FS("hostfs");
991 
992 static int __init init_hostfs(void)
993 {
994         hostfs_inode_cache = KMEM_CACHE(hostfs_inode_info, 0);
995         if (!hostfs_inode_cache)
996                 return -ENOMEM;
997         return register_filesystem(&hostfs_type);
998 }
999 
1000 static void __exit exit_hostfs(void)
1001 {
1002         unregister_filesystem(&hostfs_type);
1003         kmem_cache_destroy(hostfs_inode_cache);
1004 }
1005 
1006 module_init(init_hostfs)
1007 module_exit(exit_hostfs)
1008 MODULE_LICENSE("GPL");
1009 

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