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v4.17
  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  linux/fs/attr.c
  4 *
  5 *  Copyright (C) 1991, 1992  Linus Torvalds
  6 *  changes by Thomas Schoebel-Theuer
  7 */
  8
  9#include <linux/export.h>
 10#include <linux/time.h>
 11#include <linux/mm.h>
 12#include <linux/string.h>
 13#include <linux/sched/signal.h>
 14#include <linux/capability.h>
 15#include <linux/fsnotify.h>
 16#include <linux/fcntl.h>
 17#include <linux/security.h>
 18#include <linux/evm.h>
 19#include <linux/ima.h>
 20
 21/**
 22 * setattr_prepare - check if attribute changes to a dentry are allowed
 23 * @dentry:	dentry to check
 24 * @attr:	attributes to change
 25 *
 26 * Check if we are allowed to change the attributes contained in @attr
 27 * in the given dentry.  This includes the normal unix access permission
 28 * checks, as well as checks for rlimits and others. The function also clears
 29 * SGID bit from mode if user is not allowed to set it. Also file capabilities
 30 * and IMA extended attributes are cleared if ATTR_KILL_PRIV is set.
 31 *
 32 * Should be called as the first thing in ->setattr implementations,
 33 * possibly after taking additional locks.
 34 */
 35int setattr_prepare(struct dentry *dentry, struct iattr *attr)
 36{
 37	struct inode *inode = d_inode(dentry);
 38	unsigned int ia_valid = attr->ia_valid;
 39
 40	/*
 41	 * First check size constraints.  These can't be overriden using
 42	 * ATTR_FORCE.
 43	 */
 44	if (ia_valid & ATTR_SIZE) {
 45		int error = inode_newsize_ok(inode, attr->ia_size);
 46		if (error)
 47			return error;
 48	}
 49
 50	/* If force is set do it anyway. */
 51	if (ia_valid & ATTR_FORCE)
 52		goto kill_priv;
 53
 54	/* Make sure a caller can chown. */
 55	if ((ia_valid & ATTR_UID) &&
 56	    (!uid_eq(current_fsuid(), inode->i_uid) ||
 57	     !uid_eq(attr->ia_uid, inode->i_uid)) &&
 58	    !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
 59		return -EPERM;
 60
 61	/* Make sure caller can chgrp. */
 62	if ((ia_valid & ATTR_GID) &&
 63	    (!uid_eq(current_fsuid(), inode->i_uid) ||
 64	    (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
 65	    !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
 66		return -EPERM;
 67
 68	/* Make sure a caller can chmod. */
 69	if (ia_valid & ATTR_MODE) {
 70		if (!inode_owner_or_capable(inode))
 71			return -EPERM;
 72		/* Also check the setgid bit! */
 73		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
 74				inode->i_gid) &&
 75		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
 76			attr->ia_mode &= ~S_ISGID;
 77	}
 78
 79	/* Check for setting the inode time. */
 80	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
 81		if (!inode_owner_or_capable(inode))
 82			return -EPERM;
 83	}
 84
 85kill_priv:
 86	/* User has permission for the change */
 87	if (ia_valid & ATTR_KILL_PRIV) {
 88		int error;
 89
 90		error = security_inode_killpriv(dentry);
 91		if (error)
 92			return error;
 93	}
 94
 95	return 0;
 96}
 97EXPORT_SYMBOL(setattr_prepare);
 98
 99/**
100 * inode_newsize_ok - may this inode be truncated to a given size
101 * @inode:	the inode to be truncated
102 * @offset:	the new size to assign to the inode
103 * @Returns:	0 on success, -ve errno on failure
104 *
105 * inode_newsize_ok must be called with i_mutex held.
106 *
107 * inode_newsize_ok will check filesystem limits and ulimits to check that the
108 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
109 * when necessary. Caller must not proceed with inode size change if failure is
110 * returned. @inode must be a file (not directory), with appropriate
111 * permissions to allow truncate (inode_newsize_ok does NOT check these
112 * conditions).
113 */
114int inode_newsize_ok(const struct inode *inode, loff_t offset)
115{
116	if (inode->i_size < offset) {
117		unsigned long limit;
118
119		limit = rlimit(RLIMIT_FSIZE);
120		if (limit != RLIM_INFINITY && offset > limit)
121			goto out_sig;
122		if (offset > inode->i_sb->s_maxbytes)
123			goto out_big;
124	} else {
125		/*
126		 * truncation of in-use swapfiles is disallowed - it would
127		 * cause subsequent swapout to scribble on the now-freed
128		 * blocks.
129		 */
130		if (IS_SWAPFILE(inode))
131			return -ETXTBSY;
132	}
133
134	return 0;
135out_sig:
136	send_sig(SIGXFSZ, current, 0);
137out_big:
138	return -EFBIG;
139}
140EXPORT_SYMBOL(inode_newsize_ok);
141
142/**
143 * setattr_copy - copy simple metadata updates into the generic inode
144 * @inode:	the inode to be updated
145 * @attr:	the new attributes
146 *
147 * setattr_copy must be called with i_mutex held.
148 *
149 * setattr_copy updates the inode's metadata with that specified
150 * in attr. Noticeably missing is inode size update, which is more complex
151 * as it requires pagecache updates.
152 *
153 * The inode is not marked as dirty after this operation. The rationale is
154 * that for "simple" filesystems, the struct inode is the inode storage.
155 * The caller is free to mark the inode dirty afterwards if needed.
156 */
157void setattr_copy(struct inode *inode, const struct iattr *attr)
158{
159	unsigned int ia_valid = attr->ia_valid;
160
161	if (ia_valid & ATTR_UID)
162		inode->i_uid = attr->ia_uid;
163	if (ia_valid & ATTR_GID)
164		inode->i_gid = attr->ia_gid;
165	if (ia_valid & ATTR_ATIME)
166		inode->i_atime = timespec_trunc(attr->ia_atime,
167						inode->i_sb->s_time_gran);
168	if (ia_valid & ATTR_MTIME)
169		inode->i_mtime = timespec_trunc(attr->ia_mtime,
170						inode->i_sb->s_time_gran);
171	if (ia_valid & ATTR_CTIME)
172		inode->i_ctime = timespec_trunc(attr->ia_ctime,
173						inode->i_sb->s_time_gran);
174	if (ia_valid & ATTR_MODE) {
175		umode_t mode = attr->ia_mode;
176
177		if (!in_group_p(inode->i_gid) &&
178		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
179			mode &= ~S_ISGID;
180		inode->i_mode = mode;
181	}
182}
183EXPORT_SYMBOL(setattr_copy);
184
185/**
186 * notify_change - modify attributes of a filesytem object
187 * @dentry:	object affected
188 * @iattr:	new attributes
189 * @delegated_inode: returns inode, if the inode is delegated
190 *
191 * The caller must hold the i_mutex on the affected object.
192 *
193 * If notify_change discovers a delegation in need of breaking,
194 * it will return -EWOULDBLOCK and return a reference to the inode in
195 * delegated_inode.  The caller should then break the delegation and
196 * retry.  Because breaking a delegation may take a long time, the
197 * caller should drop the i_mutex before doing so.
198 *
199 * Alternatively, a caller may pass NULL for delegated_inode.  This may
200 * be appropriate for callers that expect the underlying filesystem not
201 * to be NFS exported.  Also, passing NULL is fine for callers holding
202 * the file open for write, as there can be no conflicting delegation in
203 * that case.
204 */
205int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
206{
207	struct inode *inode = dentry->d_inode;
208	umode_t mode = inode->i_mode;
209	int error;
210	struct timespec now;
211	unsigned int ia_valid = attr->ia_valid;
212
213	WARN_ON_ONCE(!inode_is_locked(inode));
214
215	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
216		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
217			return -EPERM;
218	}
219
220	/*
221	 * If utimes(2) and friends are called with times == NULL (or both
222	 * times are UTIME_NOW), then we need to check for write permission
223	 */
224	if (ia_valid & ATTR_TOUCH) {
225		if (IS_IMMUTABLE(inode))
226			return -EPERM;
227
228		if (!inode_owner_or_capable(inode)) {
229			error = inode_permission(inode, MAY_WRITE);
230			if (error)
231				return error;
232		}
233	}
234
235	if ((ia_valid & ATTR_MODE)) {
236		umode_t amode = attr->ia_mode;
237		/* Flag setting protected by i_mutex */
238		if (is_sxid(amode))
239			inode->i_flags &= ~S_NOSEC;
240	}
241
242	now = current_time(inode);
243
244	attr->ia_ctime = now;
245	if (!(ia_valid & ATTR_ATIME_SET))
246		attr->ia_atime = now;
247	if (!(ia_valid & ATTR_MTIME_SET))
248		attr->ia_mtime = now;
249	if (ia_valid & ATTR_KILL_PRIV) {
 
 
250		error = security_inode_need_killpriv(dentry);
251		if (error < 0)
 
 
252			return error;
253		if (error == 0)
254			ia_valid = attr->ia_valid &= ~ATTR_KILL_PRIV;
255	}
256
257	/*
258	 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
259	 * that the function has the ability to reinterpret a mode change
260	 * that's due to these bits. This adds an implicit restriction that
261	 * no function will ever call notify_change with both ATTR_MODE and
262	 * ATTR_KILL_S*ID set.
263	 */
264	if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
265	    (ia_valid & ATTR_MODE))
266		BUG();
267
268	if (ia_valid & ATTR_KILL_SUID) {
269		if (mode & S_ISUID) {
270			ia_valid = attr->ia_valid |= ATTR_MODE;
271			attr->ia_mode = (inode->i_mode & ~S_ISUID);
272		}
273	}
274	if (ia_valid & ATTR_KILL_SGID) {
275		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
276			if (!(ia_valid & ATTR_MODE)) {
277				ia_valid = attr->ia_valid |= ATTR_MODE;
278				attr->ia_mode = inode->i_mode;
279			}
280			attr->ia_mode &= ~S_ISGID;
281		}
282	}
283	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
284		return 0;
285
286	/*
287	 * Verify that uid/gid changes are valid in the target
288	 * namespace of the superblock.
289	 */
290	if (ia_valid & ATTR_UID &&
291	    !kuid_has_mapping(inode->i_sb->s_user_ns, attr->ia_uid))
292		return -EOVERFLOW;
293	if (ia_valid & ATTR_GID &&
294	    !kgid_has_mapping(inode->i_sb->s_user_ns, attr->ia_gid))
295		return -EOVERFLOW;
296
297	/* Don't allow modifications of files with invalid uids or
298	 * gids unless those uids & gids are being made valid.
299	 */
300	if (!(ia_valid & ATTR_UID) && !uid_valid(inode->i_uid))
301		return -EOVERFLOW;
302	if (!(ia_valid & ATTR_GID) && !gid_valid(inode->i_gid))
303		return -EOVERFLOW;
304
305	error = security_inode_setattr(dentry, attr);
306	if (error)
307		return error;
308	error = try_break_deleg(inode, delegated_inode);
309	if (error)
310		return error;
311
312	if (inode->i_op->setattr)
313		error = inode->i_op->setattr(dentry, attr);
314	else
315		error = simple_setattr(dentry, attr);
316
317	if (!error) {
318		fsnotify_change(dentry, ia_valid);
319		ima_inode_post_setattr(dentry);
320		evm_inode_post_setattr(dentry, ia_valid);
321	}
322
323	return error;
324}
 
325EXPORT_SYMBOL(notify_change);
v3.1
 
  1/*
  2 *  linux/fs/attr.c
  3 *
  4 *  Copyright (C) 1991, 1992  Linus Torvalds
  5 *  changes by Thomas Schoebel-Theuer
  6 */
  7
  8#include <linux/module.h>
  9#include <linux/time.h>
 10#include <linux/mm.h>
 11#include <linux/string.h>
 
 12#include <linux/capability.h>
 13#include <linux/fsnotify.h>
 14#include <linux/fcntl.h>
 15#include <linux/security.h>
 
 
 16
 17/**
 18 * inode_change_ok - check if attribute changes to an inode are allowed
 19 * @inode:	inode to check
 20 * @attr:	attributes to change
 21 *
 22 * Check if we are allowed to change the attributes contained in @attr
 23 * in the given inode.  This includes the normal unix access permission
 24 * checks, as well as checks for rlimits and others.
 
 
 25 *
 26 * Should be called as the first thing in ->setattr implementations,
 27 * possibly after taking additional locks.
 28 */
 29int inode_change_ok(const struct inode *inode, struct iattr *attr)
 30{
 
 31	unsigned int ia_valid = attr->ia_valid;
 32
 33	/*
 34	 * First check size constraints.  These can't be overriden using
 35	 * ATTR_FORCE.
 36	 */
 37	if (ia_valid & ATTR_SIZE) {
 38		int error = inode_newsize_ok(inode, attr->ia_size);
 39		if (error)
 40			return error;
 41	}
 42
 43	/* If force is set do it anyway. */
 44	if (ia_valid & ATTR_FORCE)
 45		return 0;
 46
 47	/* Make sure a caller can chown. */
 48	if ((ia_valid & ATTR_UID) &&
 49	    (current_fsuid() != inode->i_uid ||
 50	     attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
 
 51		return -EPERM;
 52
 53	/* Make sure caller can chgrp. */
 54	if ((ia_valid & ATTR_GID) &&
 55	    (current_fsuid() != inode->i_uid ||
 56	    (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) &&
 57	    !capable(CAP_CHOWN))
 58		return -EPERM;
 59
 60	/* Make sure a caller can chmod. */
 61	if (ia_valid & ATTR_MODE) {
 62		if (!inode_owner_or_capable(inode))
 63			return -EPERM;
 64		/* Also check the setgid bit! */
 65		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
 66				inode->i_gid) && !capable(CAP_FSETID))
 
 67			attr->ia_mode &= ~S_ISGID;
 68	}
 69
 70	/* Check for setting the inode time. */
 71	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
 72		if (!inode_owner_or_capable(inode))
 73			return -EPERM;
 74	}
 75
 
 
 
 
 
 
 
 
 
 
 76	return 0;
 77}
 78EXPORT_SYMBOL(inode_change_ok);
 79
 80/**
 81 * inode_newsize_ok - may this inode be truncated to a given size
 82 * @inode:	the inode to be truncated
 83 * @offset:	the new size to assign to the inode
 84 * @Returns:	0 on success, -ve errno on failure
 85 *
 86 * inode_newsize_ok must be called with i_mutex held.
 87 *
 88 * inode_newsize_ok will check filesystem limits and ulimits to check that the
 89 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
 90 * when necessary. Caller must not proceed with inode size change if failure is
 91 * returned. @inode must be a file (not directory), with appropriate
 92 * permissions to allow truncate (inode_newsize_ok does NOT check these
 93 * conditions).
 94 */
 95int inode_newsize_ok(const struct inode *inode, loff_t offset)
 96{
 97	if (inode->i_size < offset) {
 98		unsigned long limit;
 99
100		limit = rlimit(RLIMIT_FSIZE);
101		if (limit != RLIM_INFINITY && offset > limit)
102			goto out_sig;
103		if (offset > inode->i_sb->s_maxbytes)
104			goto out_big;
105	} else {
106		/*
107		 * truncation of in-use swapfiles is disallowed - it would
108		 * cause subsequent swapout to scribble on the now-freed
109		 * blocks.
110		 */
111		if (IS_SWAPFILE(inode))
112			return -ETXTBSY;
113	}
114
115	return 0;
116out_sig:
117	send_sig(SIGXFSZ, current, 0);
118out_big:
119	return -EFBIG;
120}
121EXPORT_SYMBOL(inode_newsize_ok);
122
123/**
124 * setattr_copy - copy simple metadata updates into the generic inode
125 * @inode:	the inode to be updated
126 * @attr:	the new attributes
127 *
128 * setattr_copy must be called with i_mutex held.
129 *
130 * setattr_copy updates the inode's metadata with that specified
131 * in attr. Noticeably missing is inode size update, which is more complex
132 * as it requires pagecache updates.
133 *
134 * The inode is not marked as dirty after this operation. The rationale is
135 * that for "simple" filesystems, the struct inode is the inode storage.
136 * The caller is free to mark the inode dirty afterwards if needed.
137 */
138void setattr_copy(struct inode *inode, const struct iattr *attr)
139{
140	unsigned int ia_valid = attr->ia_valid;
141
142	if (ia_valid & ATTR_UID)
143		inode->i_uid = attr->ia_uid;
144	if (ia_valid & ATTR_GID)
145		inode->i_gid = attr->ia_gid;
146	if (ia_valid & ATTR_ATIME)
147		inode->i_atime = timespec_trunc(attr->ia_atime,
148						inode->i_sb->s_time_gran);
149	if (ia_valid & ATTR_MTIME)
150		inode->i_mtime = timespec_trunc(attr->ia_mtime,
151						inode->i_sb->s_time_gran);
152	if (ia_valid & ATTR_CTIME)
153		inode->i_ctime = timespec_trunc(attr->ia_ctime,
154						inode->i_sb->s_time_gran);
155	if (ia_valid & ATTR_MODE) {
156		umode_t mode = attr->ia_mode;
157
158		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
 
159			mode &= ~S_ISGID;
160		inode->i_mode = mode;
161	}
162}
163EXPORT_SYMBOL(setattr_copy);
164
165int notify_change(struct dentry * dentry, struct iattr * attr)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
166{
167	struct inode *inode = dentry->d_inode;
168	mode_t mode = inode->i_mode;
169	int error;
170	struct timespec now;
171	unsigned int ia_valid = attr->ia_valid;
172
 
 
173	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
174		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
175			return -EPERM;
176	}
177
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
178	if ((ia_valid & ATTR_MODE)) {
179		mode_t amode = attr->ia_mode;
180		/* Flag setting protected by i_mutex */
181		if (is_sxid(amode))
182			inode->i_flags &= ~S_NOSEC;
183	}
184
185	now = current_fs_time(inode->i_sb);
186
187	attr->ia_ctime = now;
188	if (!(ia_valid & ATTR_ATIME_SET))
189		attr->ia_atime = now;
190	if (!(ia_valid & ATTR_MTIME_SET))
191		attr->ia_mtime = now;
192	if (ia_valid & ATTR_KILL_PRIV) {
193		attr->ia_valid &= ~ATTR_KILL_PRIV;
194		ia_valid &= ~ATTR_KILL_PRIV;
195		error = security_inode_need_killpriv(dentry);
196		if (error > 0)
197			error = security_inode_killpriv(dentry);
198		if (error)
199			return error;
 
 
200	}
201
202	/*
203	 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
204	 * that the function has the ability to reinterpret a mode change
205	 * that's due to these bits. This adds an implicit restriction that
206	 * no function will ever call notify_change with both ATTR_MODE and
207	 * ATTR_KILL_S*ID set.
208	 */
209	if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
210	    (ia_valid & ATTR_MODE))
211		BUG();
212
213	if (ia_valid & ATTR_KILL_SUID) {
214		if (mode & S_ISUID) {
215			ia_valid = attr->ia_valid |= ATTR_MODE;
216			attr->ia_mode = (inode->i_mode & ~S_ISUID);
217		}
218	}
219	if (ia_valid & ATTR_KILL_SGID) {
220		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
221			if (!(ia_valid & ATTR_MODE)) {
222				ia_valid = attr->ia_valid |= ATTR_MODE;
223				attr->ia_mode = inode->i_mode;
224			}
225			attr->ia_mode &= ~S_ISGID;
226		}
227	}
228	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
229		return 0;
230
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
231	error = security_inode_setattr(dentry, attr);
232	if (error)
233		return error;
 
 
 
234
235	if (inode->i_op->setattr)
236		error = inode->i_op->setattr(dentry, attr);
237	else
238		error = simple_setattr(dentry, attr);
239
240	if (!error)
241		fsnotify_change(dentry, ia_valid);
 
 
 
242
243	return error;
244}
245
246EXPORT_SYMBOL(notify_change);