xref: /openbmc/linux/fs/xattr.c (revision 3c81195a04e13833196462ab398d8bcf282701f7)
1  // SPDX-License-Identifier: GPL-2.0-only
2  /*
3    File: fs/xattr.c
4  
5    Extended attribute handling.
6  
7    Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
8    Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
9    Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
10   */
11  #include <linux/fs.h>
12  #include <linux/filelock.h>
13  #include <linux/slab.h>
14  #include <linux/file.h>
15  #include <linux/xattr.h>
16  #include <linux/mount.h>
17  #include <linux/namei.h>
18  #include <linux/security.h>
19  #include <linux/evm.h>
20  #include <linux/syscalls.h>
21  #include <linux/export.h>
22  #include <linux/fsnotify.h>
23  #include <linux/audit.h>
24  #include <linux/vmalloc.h>
25  #include <linux/posix_acl_xattr.h>
26  
27  #include <linux/uaccess.h>
28  
29  #include "internal.h"
30  
31  static const char *
32  strcmp_prefix(const char *a, const char *a_prefix)
33  {
34  	while (*a_prefix && *a == *a_prefix) {
35  		a++;
36  		a_prefix++;
37  	}
38  	return *a_prefix ? NULL : a;
39  }
40  
41  /*
42   * In order to implement different sets of xattr operations for each xattr
43   * prefix, a filesystem should create a null-terminated array of struct
44   * xattr_handler (one for each prefix) and hang a pointer to it off of the
45   * s_xattr field of the superblock.
46   */
47  #define for_each_xattr_handler(handlers, handler)		\
48  	if (handlers)						\
49  		for ((handler) = *(handlers)++;			\
50  			(handler) != NULL;			\
51  			(handler) = *(handlers)++)
52  
53  /*
54   * Find the xattr_handler with the matching prefix.
55   */
56  static const struct xattr_handler *
57  xattr_resolve_name(struct inode *inode, const char **name)
58  {
59  	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
60  	const struct xattr_handler *handler;
61  
62  	if (!(inode->i_opflags & IOP_XATTR)) {
63  		if (unlikely(is_bad_inode(inode)))
64  			return ERR_PTR(-EIO);
65  		return ERR_PTR(-EOPNOTSUPP);
66  	}
67  	for_each_xattr_handler(handlers, handler) {
68  		const char *n;
69  
70  		n = strcmp_prefix(*name, xattr_prefix(handler));
71  		if (n) {
72  			if (!handler->prefix ^ !*n) {
73  				if (*n)
74  					continue;
75  				return ERR_PTR(-EINVAL);
76  			}
77  			*name = n;
78  			return handler;
79  		}
80  	}
81  	return ERR_PTR(-EOPNOTSUPP);
82  }
83  
84  /**
85   * may_write_xattr - check whether inode allows writing xattr
86   * @idmap: idmap of the mount the inode was found from
87   * @inode: the inode on which to set an xattr
88   *
89   * Check whether the inode allows writing xattrs. Specifically, we can never
90   * set or remove an extended attribute on a read-only filesystem  or on an
91   * immutable / append-only inode.
92   *
93   * We also need to ensure that the inode has a mapping in the mount to
94   * not risk writing back invalid i_{g,u}id values.
95   *
96   * Return: On success zero is returned. On error a negative errno is returned.
97   */
98  int may_write_xattr(struct mnt_idmap *idmap, struct inode *inode)
99  {
100  	if (IS_IMMUTABLE(inode))
101  		return -EPERM;
102  	if (IS_APPEND(inode))
103  		return -EPERM;
104  	if (HAS_UNMAPPED_ID(idmap, inode))
105  		return -EPERM;
106  	return 0;
107  }
108  
109  /*
110   * Check permissions for extended attribute access.  This is a bit complicated
111   * because different namespaces have very different rules.
112   */
113  static int
114  xattr_permission(struct mnt_idmap *idmap, struct inode *inode,
115  		 const char *name, int mask)
116  {
117  	if (mask & MAY_WRITE) {
118  		int ret;
119  
120  		ret = may_write_xattr(idmap, inode);
121  		if (ret)
122  			return ret;
123  	}
124  
125  	/*
126  	 * No restriction for security.* and system.* from the VFS.  Decision
127  	 * on these is left to the underlying filesystem / security module.
128  	 */
129  	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
130  	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
131  		return 0;
132  
133  	/*
134  	 * The trusted.* namespace can only be accessed by privileged users.
135  	 */
136  	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
137  		if (!capable(CAP_SYS_ADMIN))
138  			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
139  		return 0;
140  	}
141  
142  	/*
143  	 * In the user.* namespace, only regular files and directories can have
144  	 * extended attributes. For sticky directories, only the owner and
145  	 * privileged users can write attributes.
146  	 */
147  	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
148  		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
149  			return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
150  		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
151  		    (mask & MAY_WRITE) &&
152  		    !inode_owner_or_capable(idmap, inode))
153  			return -EPERM;
154  	}
155  
156  	return inode_permission(idmap, inode, mask);
157  }
158  
159  /*
160   * Look for any handler that deals with the specified namespace.
161   */
162  int
163  xattr_supports_user_prefix(struct inode *inode)
164  {
165  	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
166  	const struct xattr_handler *handler;
167  
168  	if (!(inode->i_opflags & IOP_XATTR)) {
169  		if (unlikely(is_bad_inode(inode)))
170  			return -EIO;
171  		return -EOPNOTSUPP;
172  	}
173  
174  	for_each_xattr_handler(handlers, handler) {
175  		if (!strncmp(xattr_prefix(handler), XATTR_USER_PREFIX,
176  			     XATTR_USER_PREFIX_LEN))
177  			return 0;
178  	}
179  
180  	return -EOPNOTSUPP;
181  }
182  EXPORT_SYMBOL(xattr_supports_user_prefix);
183  
184  int
185  __vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
186  	       struct inode *inode, const char *name, const void *value,
187  	       size_t size, int flags)
188  {
189  	const struct xattr_handler *handler;
190  
191  	if (is_posix_acl_xattr(name))
192  		return -EOPNOTSUPP;
193  
194  	handler = xattr_resolve_name(inode, &name);
195  	if (IS_ERR(handler))
196  		return PTR_ERR(handler);
197  	if (!handler->set)
198  		return -EOPNOTSUPP;
199  	if (size == 0)
200  		value = "";  /* empty EA, do not remove */
201  	return handler->set(handler, idmap, dentry, inode, name, value,
202  			    size, flags);
203  }
204  EXPORT_SYMBOL(__vfs_setxattr);
205  
206  /**
207   *  __vfs_setxattr_noperm - perform setxattr operation without performing
208   *  permission checks.
209   *
210   *  @idmap: idmap of the mount the inode was found from
211   *  @dentry: object to perform setxattr on
212   *  @name: xattr name to set
213   *  @value: value to set @name to
214   *  @size: size of @value
215   *  @flags: flags to pass into filesystem operations
216   *
217   *  returns the result of the internal setxattr or setsecurity operations.
218   *
219   *  This function requires the caller to lock the inode's i_mutex before it
220   *  is executed. It also assumes that the caller will make the appropriate
221   *  permission checks.
222   */
223  int __vfs_setxattr_noperm(struct mnt_idmap *idmap,
224  			  struct dentry *dentry, const char *name,
225  			  const void *value, size_t size, int flags)
226  {
227  	struct inode *inode = dentry->d_inode;
228  	int error = -EAGAIN;
229  	int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
230  				   XATTR_SECURITY_PREFIX_LEN);
231  
232  	if (issec)
233  		inode->i_flags &= ~S_NOSEC;
234  	if (inode->i_opflags & IOP_XATTR) {
235  		error = __vfs_setxattr(idmap, dentry, inode, name, value,
236  				       size, flags);
237  		if (!error) {
238  			fsnotify_xattr(dentry);
239  			security_inode_post_setxattr(dentry, name, value,
240  						     size, flags);
241  		}
242  	} else {
243  		if (unlikely(is_bad_inode(inode)))
244  			return -EIO;
245  	}
246  	if (error == -EAGAIN) {
247  		error = -EOPNOTSUPP;
248  
249  		if (issec) {
250  			const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
251  
252  			error = security_inode_setsecurity(inode, suffix, value,
253  							   size, flags);
254  			if (!error)
255  				fsnotify_xattr(dentry);
256  		}
257  	}
258  
259  	return error;
260  }
261  
262  /**
263   * __vfs_setxattr_locked - set an extended attribute while holding the inode
264   * lock
265   *
266   *  @idmap: idmap of the mount of the target inode
267   *  @dentry: object to perform setxattr on
268   *  @name: xattr name to set
269   *  @value: value to set @name to
270   *  @size: size of @value
271   *  @flags: flags to pass into filesystem operations
272   *  @delegated_inode: on return, will contain an inode pointer that
273   *  a delegation was broken on, NULL if none.
274   */
275  int
276  __vfs_setxattr_locked(struct mnt_idmap *idmap, struct dentry *dentry,
277  		      const char *name, const void *value, size_t size,
278  		      int flags, struct inode **delegated_inode)
279  {
280  	struct inode *inode = dentry->d_inode;
281  	int error;
282  
283  	error = xattr_permission(idmap, inode, name, MAY_WRITE);
284  	if (error)
285  		return error;
286  
287  	error = security_inode_setxattr(idmap, dentry, name, value, size,
288  					flags);
289  	if (error)
290  		goto out;
291  
292  	error = try_break_deleg(inode, delegated_inode);
293  	if (error)
294  		goto out;
295  
296  	error = __vfs_setxattr_noperm(idmap, dentry, name, value,
297  				      size, flags);
298  
299  out:
300  	return error;
301  }
302  EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
303  
304  int
305  vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
306  	     const char *name, const void *value, size_t size, int flags)
307  {
308  	struct inode *inode = dentry->d_inode;
309  	struct inode *delegated_inode = NULL;
310  	const void  *orig_value = value;
311  	int error;
312  
313  	if (size && strcmp(name, XATTR_NAME_CAPS) == 0) {
314  		error = cap_convert_nscap(idmap, dentry, &value, size);
315  		if (error < 0)
316  			return error;
317  		size = error;
318  	}
319  
320  retry_deleg:
321  	inode_lock(inode);
322  	error = __vfs_setxattr_locked(idmap, dentry, name, value, size,
323  				      flags, &delegated_inode);
324  	inode_unlock(inode);
325  
326  	if (delegated_inode) {
327  		error = break_deleg_wait(&delegated_inode);
328  		if (!error)
329  			goto retry_deleg;
330  	}
331  	if (value != orig_value)
332  		kfree(value);
333  
334  	return error;
335  }
336  EXPORT_SYMBOL_GPL(vfs_setxattr);
337  
338  static ssize_t
339  xattr_getsecurity(struct mnt_idmap *idmap, struct inode *inode,
340  		  const char *name, void *value, size_t size)
341  {
342  	void *buffer = NULL;
343  	ssize_t len;
344  
345  	if (!value || !size) {
346  		len = security_inode_getsecurity(idmap, inode, name,
347  						 &buffer, false);
348  		goto out_noalloc;
349  	}
350  
351  	len = security_inode_getsecurity(idmap, inode, name, &buffer,
352  					 true);
353  	if (len < 0)
354  		return len;
355  	if (size < len) {
356  		len = -ERANGE;
357  		goto out;
358  	}
359  	memcpy(value, buffer, len);
360  out:
361  	kfree(buffer);
362  out_noalloc:
363  	return len;
364  }
365  
366  /*
367   * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
368   *
369   * Allocate memory, if not already allocated, or re-allocate correct size,
370   * before retrieving the extended attribute.  The xattr value buffer should
371   * always be freed by the caller, even on error.
372   *
373   * Returns the result of alloc, if failed, or the getxattr operation.
374   */
375  int
376  vfs_getxattr_alloc(struct mnt_idmap *idmap, struct dentry *dentry,
377  		   const char *name, char **xattr_value, size_t xattr_size,
378  		   gfp_t flags)
379  {
380  	const struct xattr_handler *handler;
381  	struct inode *inode = dentry->d_inode;
382  	char *value = *xattr_value;
383  	int error;
384  
385  	error = xattr_permission(idmap, inode, name, MAY_READ);
386  	if (error)
387  		return error;
388  
389  	handler = xattr_resolve_name(inode, &name);
390  	if (IS_ERR(handler))
391  		return PTR_ERR(handler);
392  	if (!handler->get)
393  		return -EOPNOTSUPP;
394  	error = handler->get(handler, dentry, inode, name, NULL, 0);
395  	if (error < 0)
396  		return error;
397  
398  	if (!value || (error > xattr_size)) {
399  		value = krealloc(*xattr_value, error + 1, flags);
400  		if (!value)
401  			return -ENOMEM;
402  		memset(value, 0, error + 1);
403  	}
404  
405  	error = handler->get(handler, dentry, inode, name, value, error);
406  	*xattr_value = value;
407  	return error;
408  }
409  
410  ssize_t
411  __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
412  	       void *value, size_t size)
413  {
414  	const struct xattr_handler *handler;
415  
416  	if (is_posix_acl_xattr(name))
417  		return -EOPNOTSUPP;
418  
419  	handler = xattr_resolve_name(inode, &name);
420  	if (IS_ERR(handler))
421  		return PTR_ERR(handler);
422  	if (!handler->get)
423  		return -EOPNOTSUPP;
424  	return handler->get(handler, dentry, inode, name, value, size);
425  }
426  EXPORT_SYMBOL(__vfs_getxattr);
427  
428  ssize_t
429  vfs_getxattr(struct mnt_idmap *idmap, struct dentry *dentry,
430  	     const char *name, void *value, size_t size)
431  {
432  	struct inode *inode = dentry->d_inode;
433  	int error;
434  
435  	error = xattr_permission(idmap, inode, name, MAY_READ);
436  	if (error)
437  		return error;
438  
439  	error = security_inode_getxattr(dentry, name);
440  	if (error)
441  		return error;
442  
443  	if (!strncmp(name, XATTR_SECURITY_PREFIX,
444  				XATTR_SECURITY_PREFIX_LEN)) {
445  		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
446  		int ret = xattr_getsecurity(idmap, inode, suffix, value,
447  					    size);
448  		/*
449  		 * Only overwrite the return value if a security module
450  		 * is actually active.
451  		 */
452  		if (ret == -EOPNOTSUPP)
453  			goto nolsm;
454  		return ret;
455  	}
456  nolsm:
457  	return __vfs_getxattr(dentry, inode, name, value, size);
458  }
459  EXPORT_SYMBOL_GPL(vfs_getxattr);
460  
461  /**
462   * vfs_listxattr - retrieve \0 separated list of xattr names
463   * @dentry: the dentry from whose inode the xattr names are retrieved
464   * @list: buffer to store xattr names into
465   * @size: size of the buffer
466   *
467   * This function returns the names of all xattrs associated with the
468   * inode of @dentry.
469   *
470   * Note, for legacy reasons the vfs_listxattr() function lists POSIX
471   * ACLs as well. Since POSIX ACLs are decoupled from IOP_XATTR the
472   * vfs_listxattr() function doesn't check for this flag since a
473   * filesystem could implement POSIX ACLs without implementing any other
474   * xattrs.
475   *
476   * However, since all codepaths that remove IOP_XATTR also assign of
477   * inode operations that either don't implement or implement a stub
478   * ->listxattr() operation.
479   *
480   * Return: On success, the size of the buffer that was used. On error a
481   *         negative error code.
482   */
483  ssize_t
484  vfs_listxattr(struct dentry *dentry, char *list, size_t size)
485  {
486  	struct inode *inode = d_inode(dentry);
487  	ssize_t error;
488  
489  	error = security_inode_listxattr(dentry);
490  	if (error)
491  		return error;
492  
493  	if (inode->i_op->listxattr) {
494  		error = inode->i_op->listxattr(dentry, list, size);
495  	} else {
496  		error = security_inode_listsecurity(inode, list, size);
497  		if (size && error > size)
498  			error = -ERANGE;
499  	}
500  	return error;
501  }
502  EXPORT_SYMBOL_GPL(vfs_listxattr);
503  
504  int
505  __vfs_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
506  		  const char *name)
507  {
508  	struct inode *inode = d_inode(dentry);
509  	const struct xattr_handler *handler;
510  
511  	if (is_posix_acl_xattr(name))
512  		return -EOPNOTSUPP;
513  
514  	handler = xattr_resolve_name(inode, &name);
515  	if (IS_ERR(handler))
516  		return PTR_ERR(handler);
517  	if (!handler->set)
518  		return -EOPNOTSUPP;
519  	return handler->set(handler, idmap, dentry, inode, name, NULL, 0,
520  			    XATTR_REPLACE);
521  }
522  EXPORT_SYMBOL(__vfs_removexattr);
523  
524  /**
525   * __vfs_removexattr_locked - set an extended attribute while holding the inode
526   * lock
527   *
528   *  @idmap: idmap of the mount of the target inode
529   *  @dentry: object to perform setxattr on
530   *  @name: name of xattr to remove
531   *  @delegated_inode: on return, will contain an inode pointer that
532   *  a delegation was broken on, NULL if none.
533   */
534  int
535  __vfs_removexattr_locked(struct mnt_idmap *idmap,
536  			 struct dentry *dentry, const char *name,
537  			 struct inode **delegated_inode)
538  {
539  	struct inode *inode = dentry->d_inode;
540  	int error;
541  
542  	error = xattr_permission(idmap, inode, name, MAY_WRITE);
543  	if (error)
544  		return error;
545  
546  	error = security_inode_removexattr(idmap, dentry, name);
547  	if (error)
548  		goto out;
549  
550  	error = try_break_deleg(inode, delegated_inode);
551  	if (error)
552  		goto out;
553  
554  	error = __vfs_removexattr(idmap, dentry, name);
555  
556  	if (!error) {
557  		fsnotify_xattr(dentry);
558  		evm_inode_post_removexattr(dentry, name);
559  	}
560  
561  out:
562  	return error;
563  }
564  EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
565  
566  int
567  vfs_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
568  		const char *name)
569  {
570  	struct inode *inode = dentry->d_inode;
571  	struct inode *delegated_inode = NULL;
572  	int error;
573  
574  retry_deleg:
575  	inode_lock(inode);
576  	error = __vfs_removexattr_locked(idmap, dentry,
577  					 name, &delegated_inode);
578  	inode_unlock(inode);
579  
580  	if (delegated_inode) {
581  		error = break_deleg_wait(&delegated_inode);
582  		if (!error)
583  			goto retry_deleg;
584  	}
585  
586  	return error;
587  }
588  EXPORT_SYMBOL_GPL(vfs_removexattr);
589  
590  /*
591   * Extended attribute SET operations
592   */
593  
594  int setxattr_copy(const char __user *name, struct xattr_ctx *ctx)
595  {
596  	int error;
597  
598  	if (ctx->flags & ~(XATTR_CREATE|XATTR_REPLACE))
599  		return -EINVAL;
600  
601  	error = strncpy_from_user(ctx->kname->name, name,
602  				sizeof(ctx->kname->name));
603  	if (error == 0 || error == sizeof(ctx->kname->name))
604  		return  -ERANGE;
605  	if (error < 0)
606  		return error;
607  
608  	error = 0;
609  	if (ctx->size) {
610  		if (ctx->size > XATTR_SIZE_MAX)
611  			return -E2BIG;
612  
613  		ctx->kvalue = vmemdup_user(ctx->cvalue, ctx->size);
614  		if (IS_ERR(ctx->kvalue)) {
615  			error = PTR_ERR(ctx->kvalue);
616  			ctx->kvalue = NULL;
617  		}
618  	}
619  
620  	return error;
621  }
622  
623  int do_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
624  		struct xattr_ctx *ctx)
625  {
626  	if (is_posix_acl_xattr(ctx->kname->name))
627  		return do_set_acl(idmap, dentry, ctx->kname->name,
628  				  ctx->kvalue, ctx->size);
629  
630  	return vfs_setxattr(idmap, dentry, ctx->kname->name,
631  			ctx->kvalue, ctx->size, ctx->flags);
632  }
633  
634  static long
635  setxattr(struct mnt_idmap *idmap, struct dentry *d,
636  	const char __user *name, const void __user *value, size_t size,
637  	int flags)
638  {
639  	struct xattr_name kname;
640  	struct xattr_ctx ctx = {
641  		.cvalue   = value,
642  		.kvalue   = NULL,
643  		.size     = size,
644  		.kname    = &kname,
645  		.flags    = flags,
646  	};
647  	int error;
648  
649  	error = setxattr_copy(name, &ctx);
650  	if (error)
651  		return error;
652  
653  	error = do_setxattr(idmap, d, &ctx);
654  
655  	kvfree(ctx.kvalue);
656  	return error;
657  }
658  
659  static int path_setxattr(const char __user *pathname,
660  			 const char __user *name, const void __user *value,
661  			 size_t size, int flags, unsigned int lookup_flags)
662  {
663  	struct path path;
664  	int error;
665  
666  retry:
667  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
668  	if (error)
669  		return error;
670  	error = mnt_want_write(path.mnt);
671  	if (!error) {
672  		error = setxattr(mnt_idmap(path.mnt), path.dentry, name,
673  				 value, size, flags);
674  		mnt_drop_write(path.mnt);
675  	}
676  	path_put(&path);
677  	if (retry_estale(error, lookup_flags)) {
678  		lookup_flags |= LOOKUP_REVAL;
679  		goto retry;
680  	}
681  	return error;
682  }
683  
684  SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
685  		const char __user *, name, const void __user *, value,
686  		size_t, size, int, flags)
687  {
688  	return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
689  }
690  
691  SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
692  		const char __user *, name, const void __user *, value,
693  		size_t, size, int, flags)
694  {
695  	return path_setxattr(pathname, name, value, size, flags, 0);
696  }
697  
698  SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
699  		const void __user *,value, size_t, size, int, flags)
700  {
701  	struct fd f = fdget(fd);
702  	int error = -EBADF;
703  
704  	if (!f.file)
705  		return error;
706  	audit_file(f.file);
707  	error = mnt_want_write_file(f.file);
708  	if (!error) {
709  		error = setxattr(file_mnt_idmap(f.file),
710  				 f.file->f_path.dentry, name,
711  				 value, size, flags);
712  		mnt_drop_write_file(f.file);
713  	}
714  	fdput(f);
715  	return error;
716  }
717  
718  /*
719   * Extended attribute GET operations
720   */
721  ssize_t
722  do_getxattr(struct mnt_idmap *idmap, struct dentry *d,
723  	struct xattr_ctx *ctx)
724  {
725  	ssize_t error;
726  	char *kname = ctx->kname->name;
727  
728  	if (ctx->size) {
729  		if (ctx->size > XATTR_SIZE_MAX)
730  			ctx->size = XATTR_SIZE_MAX;
731  		ctx->kvalue = kvzalloc(ctx->size, GFP_KERNEL);
732  		if (!ctx->kvalue)
733  			return -ENOMEM;
734  	}
735  
736  	if (is_posix_acl_xattr(ctx->kname->name))
737  		error = do_get_acl(idmap, d, kname, ctx->kvalue, ctx->size);
738  	else
739  		error = vfs_getxattr(idmap, d, kname, ctx->kvalue, ctx->size);
740  	if (error > 0) {
741  		if (ctx->size && copy_to_user(ctx->value, ctx->kvalue, error))
742  			error = -EFAULT;
743  	} else if (error == -ERANGE && ctx->size >= XATTR_SIZE_MAX) {
744  		/* The file system tried to returned a value bigger
745  		   than XATTR_SIZE_MAX bytes. Not possible. */
746  		error = -E2BIG;
747  	}
748  
749  	return error;
750  }
751  
752  static ssize_t
753  getxattr(struct mnt_idmap *idmap, struct dentry *d,
754  	 const char __user *name, void __user *value, size_t size)
755  {
756  	ssize_t error;
757  	struct xattr_name kname;
758  	struct xattr_ctx ctx = {
759  		.value    = value,
760  		.kvalue   = NULL,
761  		.size     = size,
762  		.kname    = &kname,
763  		.flags    = 0,
764  	};
765  
766  	error = strncpy_from_user(kname.name, name, sizeof(kname.name));
767  	if (error == 0 || error == sizeof(kname.name))
768  		error = -ERANGE;
769  	if (error < 0)
770  		return error;
771  
772  	error =  do_getxattr(idmap, d, &ctx);
773  
774  	kvfree(ctx.kvalue);
775  	return error;
776  }
777  
778  static ssize_t path_getxattr(const char __user *pathname,
779  			     const char __user *name, void __user *value,
780  			     size_t size, unsigned int lookup_flags)
781  {
782  	struct path path;
783  	ssize_t error;
784  retry:
785  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
786  	if (error)
787  		return error;
788  	error = getxattr(mnt_idmap(path.mnt), path.dentry, name, value, size);
789  	path_put(&path);
790  	if (retry_estale(error, lookup_flags)) {
791  		lookup_flags |= LOOKUP_REVAL;
792  		goto retry;
793  	}
794  	return error;
795  }
796  
797  SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
798  		const char __user *, name, void __user *, value, size_t, size)
799  {
800  	return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
801  }
802  
803  SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
804  		const char __user *, name, void __user *, value, size_t, size)
805  {
806  	return path_getxattr(pathname, name, value, size, 0);
807  }
808  
809  SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
810  		void __user *, value, size_t, size)
811  {
812  	struct fd f = fdget(fd);
813  	ssize_t error = -EBADF;
814  
815  	if (!f.file)
816  		return error;
817  	audit_file(f.file);
818  	error = getxattr(file_mnt_idmap(f.file), f.file->f_path.dentry,
819  			 name, value, size);
820  	fdput(f);
821  	return error;
822  }
823  
824  /*
825   * Extended attribute LIST operations
826   */
827  static ssize_t
828  listxattr(struct dentry *d, char __user *list, size_t size)
829  {
830  	ssize_t error;
831  	char *klist = NULL;
832  
833  	if (size) {
834  		if (size > XATTR_LIST_MAX)
835  			size = XATTR_LIST_MAX;
836  		klist = kvmalloc(size, GFP_KERNEL);
837  		if (!klist)
838  			return -ENOMEM;
839  	}
840  
841  	error = vfs_listxattr(d, klist, size);
842  	if (error > 0) {
843  		if (size && copy_to_user(list, klist, error))
844  			error = -EFAULT;
845  	} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
846  		/* The file system tried to returned a list bigger
847  		   than XATTR_LIST_MAX bytes. Not possible. */
848  		error = -E2BIG;
849  	}
850  
851  	kvfree(klist);
852  
853  	return error;
854  }
855  
856  static ssize_t path_listxattr(const char __user *pathname, char __user *list,
857  			      size_t size, unsigned int lookup_flags)
858  {
859  	struct path path;
860  	ssize_t error;
861  retry:
862  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
863  	if (error)
864  		return error;
865  	error = listxattr(path.dentry, list, size);
866  	path_put(&path);
867  	if (retry_estale(error, lookup_flags)) {
868  		lookup_flags |= LOOKUP_REVAL;
869  		goto retry;
870  	}
871  	return error;
872  }
873  
874  SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
875  		size_t, size)
876  {
877  	return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
878  }
879  
880  SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
881  		size_t, size)
882  {
883  	return path_listxattr(pathname, list, size, 0);
884  }
885  
886  SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
887  {
888  	struct fd f = fdget(fd);
889  	ssize_t error = -EBADF;
890  
891  	if (!f.file)
892  		return error;
893  	audit_file(f.file);
894  	error = listxattr(f.file->f_path.dentry, list, size);
895  	fdput(f);
896  	return error;
897  }
898  
899  /*
900   * Extended attribute REMOVE operations
901   */
902  static long
903  removexattr(struct mnt_idmap *idmap, struct dentry *d,
904  	    const char __user *name)
905  {
906  	int error;
907  	char kname[XATTR_NAME_MAX + 1];
908  
909  	error = strncpy_from_user(kname, name, sizeof(kname));
910  	if (error == 0 || error == sizeof(kname))
911  		error = -ERANGE;
912  	if (error < 0)
913  		return error;
914  
915  	if (is_posix_acl_xattr(kname))
916  		return vfs_remove_acl(idmap, d, kname);
917  
918  	return vfs_removexattr(idmap, d, kname);
919  }
920  
921  static int path_removexattr(const char __user *pathname,
922  			    const char __user *name, unsigned int lookup_flags)
923  {
924  	struct path path;
925  	int error;
926  retry:
927  	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
928  	if (error)
929  		return error;
930  	error = mnt_want_write(path.mnt);
931  	if (!error) {
932  		error = removexattr(mnt_idmap(path.mnt), path.dentry, name);
933  		mnt_drop_write(path.mnt);
934  	}
935  	path_put(&path);
936  	if (retry_estale(error, lookup_flags)) {
937  		lookup_flags |= LOOKUP_REVAL;
938  		goto retry;
939  	}
940  	return error;
941  }
942  
943  SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
944  		const char __user *, name)
945  {
946  	return path_removexattr(pathname, name, LOOKUP_FOLLOW);
947  }
948  
949  SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
950  		const char __user *, name)
951  {
952  	return path_removexattr(pathname, name, 0);
953  }
954  
955  SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
956  {
957  	struct fd f = fdget(fd);
958  	int error = -EBADF;
959  
960  	if (!f.file)
961  		return error;
962  	audit_file(f.file);
963  	error = mnt_want_write_file(f.file);
964  	if (!error) {
965  		error = removexattr(file_mnt_idmap(f.file),
966  				    f.file->f_path.dentry, name);
967  		mnt_drop_write_file(f.file);
968  	}
969  	fdput(f);
970  	return error;
971  }
972  
973  int xattr_list_one(char **buffer, ssize_t *remaining_size, const char *name)
974  {
975  	size_t len;
976  
977  	len = strlen(name) + 1;
978  	if (*buffer) {
979  		if (*remaining_size < len)
980  			return -ERANGE;
981  		memcpy(*buffer, name, len);
982  		*buffer += len;
983  	}
984  	*remaining_size -= len;
985  	return 0;
986  }
987  
988  /**
989   * generic_listxattr - run through a dentry's xattr list() operations
990   * @dentry: dentry to list the xattrs
991   * @buffer: result buffer
992   * @buffer_size: size of @buffer
993   *
994   * Combine the results of the list() operation from every xattr_handler in the
995   * xattr_handler stack.
996   *
997   * Note that this will not include the entries for POSIX ACLs.
998   */
999  ssize_t
1000  generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
1001  {
1002  	const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
1003  	ssize_t remaining_size = buffer_size;
1004  	int err = 0;
1005  
1006  	for_each_xattr_handler(handlers, handler) {
1007  		if (!handler->name || (handler->list && !handler->list(dentry)))
1008  			continue;
1009  		err = xattr_list_one(&buffer, &remaining_size, handler->name);
1010  		if (err)
1011  			return err;
1012  	}
1013  
1014  	return err ? err : buffer_size - remaining_size;
1015  }
1016  EXPORT_SYMBOL(generic_listxattr);
1017  
1018  /**
1019   * xattr_full_name  -  Compute full attribute name from suffix
1020   *
1021   * @handler:	handler of the xattr_handler operation
1022   * @name:	name passed to the xattr_handler operation
1023   *
1024   * The get and set xattr handler operations are called with the remainder of
1025   * the attribute name after skipping the handler's prefix: for example, "foo"
1026   * is passed to the get operation of a handler with prefix "user." to get
1027   * attribute "user.foo".  The full name is still "there" in the name though.
1028   *
1029   * Note: the list xattr handler operation when called from the vfs is passed a
1030   * NULL name; some file systems use this operation internally, with varying
1031   * semantics.
1032   */
1033  const char *xattr_full_name(const struct xattr_handler *handler,
1034  			    const char *name)
1035  {
1036  	size_t prefix_len = strlen(xattr_prefix(handler));
1037  
1038  	return name - prefix_len;
1039  }
1040  EXPORT_SYMBOL(xattr_full_name);
1041  
1042  /**
1043   * free_simple_xattr - free an xattr object
1044   * @xattr: the xattr object
1045   *
1046   * Free the xattr object. Can handle @xattr being NULL.
1047   */
1048  static inline void free_simple_xattr(struct simple_xattr *xattr)
1049  {
1050  	if (xattr)
1051  		kfree(xattr->name);
1052  	kvfree(xattr);
1053  }
1054  
1055  /**
1056   * simple_xattr_alloc - allocate new xattr object
1057   * @value: value of the xattr object
1058   * @size: size of @value
1059   *
1060   * Allocate a new xattr object and initialize respective members. The caller is
1061   * responsible for handling the name of the xattr.
1062   *
1063   * Return: On success a new xattr object is returned. On failure NULL is
1064   * returned.
1065   */
1066  struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
1067  {
1068  	struct simple_xattr *new_xattr;
1069  	size_t len;
1070  
1071  	/* wrap around? */
1072  	len = sizeof(*new_xattr) + size;
1073  	if (len < sizeof(*new_xattr))
1074  		return NULL;
1075  
1076  	new_xattr = kvmalloc(len, GFP_KERNEL);
1077  	if (!new_xattr)
1078  		return NULL;
1079  
1080  	new_xattr->size = size;
1081  	memcpy(new_xattr->value, value, size);
1082  	return new_xattr;
1083  }
1084  
1085  /**
1086   * rbtree_simple_xattr_cmp - compare xattr name with current rbtree xattr entry
1087   * @key: xattr name
1088   * @node: current node
1089   *
1090   * Compare the xattr name with the xattr name attached to @node in the rbtree.
1091   *
1092   * Return: Negative value if continuing left, positive if continuing right, 0
1093   * if the xattr attached to @node matches @key.
1094   */
1095  static int rbtree_simple_xattr_cmp(const void *key, const struct rb_node *node)
1096  {
1097  	const char *xattr_name = key;
1098  	const struct simple_xattr *xattr;
1099  
1100  	xattr = rb_entry(node, struct simple_xattr, rb_node);
1101  	return strcmp(xattr->name, xattr_name);
1102  }
1103  
1104  /**
1105   * rbtree_simple_xattr_node_cmp - compare two xattr rbtree nodes
1106   * @new_node: new node
1107   * @node: current node
1108   *
1109   * Compare the xattr attached to @new_node with the xattr attached to @node.
1110   *
1111   * Return: Negative value if continuing left, positive if continuing right, 0
1112   * if the xattr attached to @new_node matches the xattr attached to @node.
1113   */
1114  static int rbtree_simple_xattr_node_cmp(struct rb_node *new_node,
1115  					const struct rb_node *node)
1116  {
1117  	struct simple_xattr *xattr;
1118  	xattr = rb_entry(new_node, struct simple_xattr, rb_node);
1119  	return rbtree_simple_xattr_cmp(xattr->name, node);
1120  }
1121  
1122  /**
1123   * simple_xattr_get - get an xattr object
1124   * @xattrs: the header of the xattr object
1125   * @name: the name of the xattr to retrieve
1126   * @buffer: the buffer to store the value into
1127   * @size: the size of @buffer
1128   *
1129   * Try to find and retrieve the xattr object associated with @name.
1130   * If @buffer is provided store the value of @xattr in @buffer
1131   * otherwise just return the length. The size of @buffer is limited
1132   * to XATTR_SIZE_MAX which currently is 65536.
1133   *
1134   * Return: On success the length of the xattr value is returned. On error a
1135   * negative error code is returned.
1136   */
1137  int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
1138  		     void *buffer, size_t size)
1139  {
1140  	struct simple_xattr *xattr = NULL;
1141  	struct rb_node *rbp;
1142  	int ret = -ENODATA;
1143  
1144  	read_lock(&xattrs->lock);
1145  	rbp = rb_find(name, &xattrs->rb_root, rbtree_simple_xattr_cmp);
1146  	if (rbp) {
1147  		xattr = rb_entry(rbp, struct simple_xattr, rb_node);
1148  		ret = xattr->size;
1149  		if (buffer) {
1150  			if (size < xattr->size)
1151  				ret = -ERANGE;
1152  			else
1153  				memcpy(buffer, xattr->value, xattr->size);
1154  		}
1155  	}
1156  	read_unlock(&xattrs->lock);
1157  	return ret;
1158  }
1159  
1160  /**
1161   * simple_xattr_set - set an xattr object
1162   * @xattrs: the header of the xattr object
1163   * @name: the name of the xattr to retrieve
1164   * @value: the value to store along the xattr
1165   * @size: the size of @value
1166   * @flags: the flags determining how to set the xattr
1167   * @removed_size: the size of the removed xattr
1168   *
1169   * Set a new xattr object.
1170   * If @value is passed a new xattr object will be allocated. If XATTR_REPLACE
1171   * is specified in @flags a matching xattr object for @name must already exist.
1172   * If it does it will be replaced with the new xattr object. If it doesn't we
1173   * fail. If XATTR_CREATE is specified and a matching xattr does already exist
1174   * we fail. If it doesn't we create a new xattr. If @flags is zero we simply
1175   * insert the new xattr replacing any existing one.
1176   *
1177   * If @value is empty and a matching xattr object is found we delete it if
1178   * XATTR_REPLACE is specified in @flags or @flags is zero.
1179   *
1180   * If @value is empty and no matching xattr object for @name is found we do
1181   * nothing if XATTR_CREATE is specified in @flags or @flags is zero. For
1182   * XATTR_REPLACE we fail as mentioned above.
1183   *
1184   * Return: On success zero and on error a negative error code is returned.
1185   */
1186  int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
1187  		     const void *value, size_t size, int flags,
1188  		     ssize_t *removed_size)
1189  {
1190  	struct simple_xattr *xattr = NULL, *new_xattr = NULL;
1191  	struct rb_node *parent = NULL, **rbp;
1192  	int err = 0, ret;
1193  
1194  	if (removed_size)
1195  		*removed_size = -1;
1196  
1197  	/* value == NULL means remove */
1198  	if (value) {
1199  		new_xattr = simple_xattr_alloc(value, size);
1200  		if (!new_xattr)
1201  			return -ENOMEM;
1202  
1203  		new_xattr->name = kstrdup(name, GFP_KERNEL);
1204  		if (!new_xattr->name) {
1205  			free_simple_xattr(new_xattr);
1206  			return -ENOMEM;
1207  		}
1208  	}
1209  
1210  	write_lock(&xattrs->lock);
1211  	rbp = &xattrs->rb_root.rb_node;
1212  	while (*rbp) {
1213  		parent = *rbp;
1214  		ret = rbtree_simple_xattr_cmp(name, *rbp);
1215  		if (ret < 0)
1216  			rbp = &(*rbp)->rb_left;
1217  		else if (ret > 0)
1218  			rbp = &(*rbp)->rb_right;
1219  		else
1220  			xattr = rb_entry(*rbp, struct simple_xattr, rb_node);
1221  		if (xattr)
1222  			break;
1223  	}
1224  
1225  	if (xattr) {
1226  		/* Fail if XATTR_CREATE is requested and the xattr exists. */
1227  		if (flags & XATTR_CREATE) {
1228  			err = -EEXIST;
1229  			goto out_unlock;
1230  		}
1231  
1232  		if (new_xattr)
1233  			rb_replace_node(&xattr->rb_node, &new_xattr->rb_node,
1234  					&xattrs->rb_root);
1235  		else
1236  			rb_erase(&xattr->rb_node, &xattrs->rb_root);
1237  		if (!err && removed_size)
1238  			*removed_size = xattr->size;
1239  	} else {
1240  		/* Fail if XATTR_REPLACE is requested but no xattr is found. */
1241  		if (flags & XATTR_REPLACE) {
1242  			err = -ENODATA;
1243  			goto out_unlock;
1244  		}
1245  
1246  		/*
1247  		 * If XATTR_CREATE or no flags are specified together with a
1248  		 * new value simply insert it.
1249  		 */
1250  		if (new_xattr) {
1251  			rb_link_node(&new_xattr->rb_node, parent, rbp);
1252  			rb_insert_color(&new_xattr->rb_node, &xattrs->rb_root);
1253  		}
1254  
1255  		/*
1256  		 * If XATTR_CREATE or no flags are specified and neither an
1257  		 * old or new xattr exist then we don't need to do anything.
1258  		 */
1259  	}
1260  
1261  out_unlock:
1262  	write_unlock(&xattrs->lock);
1263  	if (err)
1264  		free_simple_xattr(new_xattr);
1265  	else
1266  		free_simple_xattr(xattr);
1267  	return err;
1268  
1269  }
1270  
1271  static bool xattr_is_trusted(const char *name)
1272  {
1273  	return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
1274  }
1275  
1276  /**
1277   * simple_xattr_list - list all xattr objects
1278   * @inode: inode from which to get the xattrs
1279   * @xattrs: the header of the xattr object
1280   * @buffer: the buffer to store all xattrs into
1281   * @size: the size of @buffer
1282   *
1283   * List all xattrs associated with @inode. If @buffer is NULL we returned
1284   * the required size of the buffer. If @buffer is provided we store the
1285   * xattrs value into it provided it is big enough.
1286   *
1287   * Note, the number of xattr names that can be listed with listxattr(2) is
1288   * limited to XATTR_LIST_MAX aka 65536 bytes. If a larger buffer is passed
1289   * then vfs_listxattr() caps it to XATTR_LIST_MAX and if more xattr names
1290   * are found it will return -E2BIG.
1291   *
1292   * Return: On success the required size or the size of the copied xattrs is
1293   * returned. On error a negative error code is returned.
1294   */
1295  ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1296  			  char *buffer, size_t size)
1297  {
1298  	bool trusted = ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
1299  	struct simple_xattr *xattr;
1300  	struct rb_node *rbp;
1301  	ssize_t remaining_size = size;
1302  	int err = 0;
1303  
1304  	err = posix_acl_listxattr(inode, &buffer, &remaining_size);
1305  	if (err)
1306  		return err;
1307  
1308  	read_lock(&xattrs->lock);
1309  	for (rbp = rb_first(&xattrs->rb_root); rbp; rbp = rb_next(rbp)) {
1310  		xattr = rb_entry(rbp, struct simple_xattr, rb_node);
1311  
1312  		/* skip "trusted." attributes for unprivileged callers */
1313  		if (!trusted && xattr_is_trusted(xattr->name))
1314  			continue;
1315  
1316  		err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1317  		if (err)
1318  			break;
1319  	}
1320  	read_unlock(&xattrs->lock);
1321  
1322  	return err ? err : size - remaining_size;
1323  }
1324  
1325  /**
1326   * rbtree_simple_xattr_less - compare two xattr rbtree nodes
1327   * @new_node: new node
1328   * @node: current node
1329   *
1330   * Compare the xattr attached to @new_node with the xattr attached to @node.
1331   * Note that this function technically tolerates duplicate entries.
1332   *
1333   * Return: True if insertion point in the rbtree is found.
1334   */
1335  static bool rbtree_simple_xattr_less(struct rb_node *new_node,
1336  				     const struct rb_node *node)
1337  {
1338  	return rbtree_simple_xattr_node_cmp(new_node, node) < 0;
1339  }
1340  
1341  /**
1342   * simple_xattr_add - add xattr objects
1343   * @xattrs: the header of the xattr object
1344   * @new_xattr: the xattr object to add
1345   *
1346   * Add an xattr object to @xattrs. This assumes no replacement or removal
1347   * of matching xattrs is wanted. Should only be called during inode
1348   * initialization when a few distinct initial xattrs are supposed to be set.
1349   */
1350  void simple_xattr_add(struct simple_xattrs *xattrs,
1351  		      struct simple_xattr *new_xattr)
1352  {
1353  	write_lock(&xattrs->lock);
1354  	rb_add(&new_xattr->rb_node, &xattrs->rb_root, rbtree_simple_xattr_less);
1355  	write_unlock(&xattrs->lock);
1356  }
1357  
1358  /**
1359   * simple_xattrs_init - initialize new xattr header
1360   * @xattrs: header to initialize
1361   *
1362   * Initialize relevant fields of a an xattr header.
1363   */
1364  void simple_xattrs_init(struct simple_xattrs *xattrs)
1365  {
1366  	xattrs->rb_root = RB_ROOT;
1367  	rwlock_init(&xattrs->lock);
1368  }
1369  
1370  /**
1371   * simple_xattrs_free - free xattrs
1372   * @xattrs: xattr header whose xattrs to destroy
1373   *
1374   * Destroy all xattrs in @xattr. When this is called no one can hold a
1375   * reference to any of the xattrs anymore.
1376   */
1377  void simple_xattrs_free(struct simple_xattrs *xattrs)
1378  {
1379  	struct rb_node *rbp;
1380  
1381  	rbp = rb_first(&xattrs->rb_root);
1382  	while (rbp) {
1383  		struct simple_xattr *xattr;
1384  		struct rb_node *rbp_next;
1385  
1386  		rbp_next = rb_next(rbp);
1387  		xattr = rb_entry(rbp, struct simple_xattr, rb_node);
1388  		rb_erase(&xattr->rb_node, &xattrs->rb_root);
1389  		free_simple_xattr(xattr);
1390  		rbp = rbp_next;
1391  	}
1392  }
1393