[mirror_ubuntu-bionic-kernel.git] / fs / attr.c

/*
 *  linux/fs/attr.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  changes by Thomas Schoebel-Theuer
 */

#include <linux/export.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/capability.h>
#include <linux/fsnotify.h>
#include <linux/fcntl.h>
#include <linux/security.h>
#include <linux/evm.h>
#include <linux/ima.h>

/**
 * inode_change_ok - check if attribute changes to an inode are allowed
 * @inode:	inode to check
 * @attr:	attributes to change
 *
 * Check if we are allowed to change the attributes contained in @attr
 * in the given inode.  This includes the normal unix access permission
 * checks, as well as checks for rlimits and others.
 *
 * Should be called as the first thing in ->setattr implementations,
 * possibly after taking additional locks.
 */
int inode_change_ok(const struct inode *inode, struct iattr *attr)
{
	unsigned int ia_valid = attr->ia_valid;

	/*
	 * First check size constraints.  These can't be overriden using
	 * ATTR_FORCE.
	 */
	if (ia_valid & ATTR_SIZE) {
		int error = inode_newsize_ok(inode, attr->ia_size);
		if (error)
			return error;
	}

	/* If force is set do it anyway. */
	if (ia_valid & ATTR_FORCE)
		return 0;

	/* Make sure a caller can chown. */
	if ((ia_valid & ATTR_UID) &&
	    (!uid_eq(current_fsuid(), inode->i_uid) ||
	     !uid_eq(attr->ia_uid, inode->i_uid)) &&
	    !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
		return -EPERM;

	/* Make sure caller can chgrp. */
	if ((ia_valid & ATTR_GID) &&
	    (!uid_eq(current_fsuid(), inode->i_uid) ||
	    (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
	    !capable_wrt_inode_uidgid(inode, CAP_CHOWN))
		return -EPERM;

	/* Make sure a caller can chmod. */
	if (ia_valid & ATTR_MODE) {
		if (!inode_owner_or_capable(inode))
			return -EPERM;
		/* Also check the setgid bit! */
		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
				inode->i_gid) &&
		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
			attr->ia_mode &= ~S_ISGID;
	}

	/* Check for setting the inode time. */
	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
		if (!inode_owner_or_capable(inode))
			return -EPERM;
	}

	return 0;
}
EXPORT_SYMBOL(inode_change_ok);

/**
 * inode_newsize_ok - may this inode be truncated to a given size
 * @inode:	the inode to be truncated
 * @offset:	the new size to assign to the inode
 * @Returns:	0 on success, -ve errno on failure
 *
 * inode_newsize_ok must be called with i_mutex held.
 *
 * inode_newsize_ok will check filesystem limits and ulimits to check that the
 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
 * when necessary. Caller must not proceed with inode size change if failure is
 * returned. @inode must be a file (not directory), with appropriate
 * permissions to allow truncate (inode_newsize_ok does NOT check these
 * conditions).
 */
int inode_newsize_ok(const struct inode *inode, loff_t offset)
{
	if (inode->i_size < offset) {
		unsigned long limit;

		limit = rlimit(RLIMIT_FSIZE);
		if (limit != RLIM_INFINITY && offset > limit)
			goto out_sig;
		if (offset > inode->i_sb->s_maxbytes)
			goto out_big;
	} else {
		/*
		 * truncation of in-use swapfiles is disallowed - it would
		 * cause subsequent swapout to scribble on the now-freed
		 * blocks.
		 */
		if (IS_SWAPFILE(inode))
			return -ETXTBSY;
	}

	return 0;
out_sig:
	send_sig(SIGXFSZ, current, 0);
out_big:
	return -EFBIG;
}
EXPORT_SYMBOL(inode_newsize_ok);

/**
 * setattr_copy - copy simple metadata updates into the generic inode
 * @inode:	the inode to be updated
 * @attr:	the new attributes
 *
 * setattr_copy must be called with i_mutex held.
 *
 * setattr_copy updates the inode's metadata with that specified
 * in attr. Noticeably missing is inode size update, which is more complex
 * as it requires pagecache updates.
 *
 * The inode is not marked as dirty after this operation. The rationale is
 * that for "simple" filesystems, the struct inode is the inode storage.
 * The caller is free to mark the inode dirty afterwards if needed.
 */
void setattr_copy(struct inode *inode, const struct iattr *attr)
{
	unsigned int ia_valid = attr->ia_valid;

	if (ia_valid & ATTR_UID)
		inode->i_uid = attr->ia_uid;
	if (ia_valid & ATTR_GID)
		inode->i_gid = attr->ia_gid;
	if (ia_valid & ATTR_ATIME)
		inode->i_atime = timespec_trunc(attr->ia_atime,
						inode->i_sb->s_time_gran);
	if (ia_valid & ATTR_MTIME)
		inode->i_mtime = timespec_trunc(attr->ia_mtime,
						inode->i_sb->s_time_gran);
	if (ia_valid & ATTR_CTIME)
		inode->i_ctime = timespec_trunc(attr->ia_ctime,
						inode->i_sb->s_time_gran);
	if (ia_valid & ATTR_MODE) {
		umode_t mode = attr->ia_mode;

		if (!in_group_p(inode->i_gid) &&
		    !capable_wrt_inode_uidgid(inode, CAP_FSETID))
			mode &= ~S_ISGID;
		inode->i_mode = mode;
	}
}
EXPORT_SYMBOL(setattr_copy);

/**
 * notify_change - modify attributes of a filesytem object
 * @dentry:	object affected
 * @iattr:	new attributes
 * @delegated_inode: returns inode, if the inode is delegated
 *
 * The caller must hold the i_mutex on the affected object.
 *
 * If notify_change discovers a delegation in need of breaking,
 * it will return -EWOULDBLOCK and return a reference to the inode in
 * delegated_inode.  The caller should then break the delegation and
 * retry.  Because breaking a delegation may take a long time, the
 * caller should drop the i_mutex before doing so.
 *
 * Alternatively, a caller may pass NULL for delegated_inode.  This may
 * be appropriate for callers that expect the underlying filesystem not
 * to be NFS exported.  Also, passing NULL is fine for callers holding
 * the file open for write, as there can be no conflicting delegation in
 * that case.
 */
int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
{
	struct inode *inode = dentry->d_inode;
	umode_t mode = inode->i_mode;
	int error;
	struct timespec now;
	unsigned int ia_valid = attr->ia_valid;

	WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));

	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
			return -EPERM;
	}

	if ((ia_valid & ATTR_MODE)) {
		umode_t amode = attr->ia_mode;
		/* Flag setting protected by i_mutex */
		if (is_sxid(amode))
			inode->i_flags &= ~S_NOSEC;
	}

	now = current_fs_time(inode->i_sb);

	attr->ia_ctime = now;
	if (!(ia_valid & ATTR_ATIME_SET))
		attr->ia_atime = now;
	if (!(ia_valid & ATTR_MTIME_SET))
		attr->ia_mtime = now;
	if (ia_valid & ATTR_KILL_PRIV) {
		attr->ia_valid &= ~ATTR_KILL_PRIV;
		ia_valid &= ~ATTR_KILL_PRIV;
		error = security_inode_need_killpriv(dentry);
		if (error > 0)
			error = security_inode_killpriv(dentry);
		if (error)
			return error;
	}

	/*
	 * We now pass ATTR_KILL_S*ID to the lower level setattr function so
	 * that the function has the ability to reinterpret a mode change
	 * that's due to these bits. This adds an implicit restriction that
	 * no function will ever call notify_change with both ATTR_MODE and
	 * ATTR_KILL_S*ID set.
	 */
	if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
	    (ia_valid & ATTR_MODE))
		BUG();

	if (ia_valid & ATTR_KILL_SUID) {
		if (mode & S_ISUID) {
			ia_valid = attr->ia_valid |= ATTR_MODE;
			attr->ia_mode = (inode->i_mode & ~S_ISUID);
		}
	}
	if (ia_valid & ATTR_KILL_SGID) {
		if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
			if (!(ia_valid & ATTR_MODE)) {
				ia_valid = attr->ia_valid |= ATTR_MODE;
				attr->ia_mode = inode->i_mode;
			}
			attr->ia_mode &= ~S_ISGID;
		}
	}
	if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
		return 0;

	error = security_inode_setattr(dentry, attr);
	if (error)
		return error;
	error = try_break_deleg(inode, delegated_inode);
	if (error)
		return error;

	if (inode->i_op->setattr)
		error = inode->i_op->setattr(dentry, attr);
	else
		error = simple_setattr(dentry, attr);

	if (!error) {
		fsnotify_change(dentry, ia_valid);
		ima_inode_post_setattr(dentry);
		evm_inode_post_setattr(dentry, ia_valid);
	}

	return error;
}
EXPORT_SYMBOL(notify_change);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/attr.c
	3	*
	4	* Copyright (C) 1991, 1992 Linus Torvalds
	5	* changes by Thomas Schoebel-Theuer
	6	*/
	7
630d9c47	8	#include <linux/export.h>
1da177e4 LT	9	#include <linux/time.h>
	10	#include <linux/mm.h>
	11	#include <linux/string.h>
16f7e0fe	12	#include <linux/capability.h>
0eeca283	13	#include <linux/fsnotify.h>
1da177e4	14	#include <linux/fcntl.h>
1da177e4	15	#include <linux/security.h>
975d2943	16	#include <linux/evm.h>
9957a504	17	#include <linux/ima.h>
1da177e4	18
2c27c65e CH	19	/**
	20	* inode_change_ok - check if attribute changes to an inode are allowed
	21	* @inode: inode to check
	22	* @attr: attributes to change
	23	*
	24	* Check if we are allowed to change the attributes contained in @attr
	25	* in the given inode. This includes the normal unix access permission
	26	* checks, as well as checks for rlimits and others.
	27	*
	28	* Should be called as the first thing in ->setattr implementations,
	29	* possibly after taking additional locks.
	30	*/
25d9e2d1	31	int inode_change_ok(const struct inode inode, struct iattr attr)
1da177e4	32	{
1da177e4 LT	33	unsigned int ia_valid = attr->ia_valid;
1da177e4 LT	34
2c27c65e CH	35	/*
	36	* First check size constraints. These can't be overriden using
	37	* ATTR_FORCE.
	38	*/
	39	if (ia_valid & ATTR_SIZE) {
	40	int error = inode_newsize_ok(inode, attr->ia_size);
	41	if (error)
	42	return error;
	43	}
	44
1da177e4 LT	45	/* If force is set do it anyway. */
1da177e4 LT	46	if (ia_valid & ATTR_FORCE)
2c27c65e	47	return 0;
1da177e4 LT	48
	49	/* Make sure a caller can chown. */
	50	if ((ia_valid & ATTR_UID) &&
8e96e3b7	51	(!uid_eq(current_fsuid(), inode->i_uid) \|\|
7fa294c8	52	!uid_eq(attr->ia_uid, inode->i_uid)) &&
23adbe12	53	!capable_wrt_inode_uidgid(inode, CAP_CHOWN))
2c27c65e	54	return -EPERM;
1da177e4 LT	55
	56	/* Make sure caller can chgrp. */
	57	if ((ia_valid & ATTR_GID) &&
8e96e3b7 EB	58	(!uid_eq(current_fsuid(), inode->i_uid) \|\|
8e96e3b7 EB	59	(!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
23adbe12	60	!capable_wrt_inode_uidgid(inode, CAP_CHOWN))
2c27c65e	61	return -EPERM;
1da177e4 LT	62
	63	/* Make sure a caller can chmod. */
	64	if (ia_valid & ATTR_MODE) {
2e149670	65	if (!inode_owner_or_capable(inode))
2c27c65e	66	return -EPERM;
1da177e4 LT	67	/* Also check the setgid bit! */
1da177e4 LT	68	if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
7fa294c8	69	inode->i_gid) &&
23adbe12	70	!capable_wrt_inode_uidgid(inode, CAP_FSETID))
1da177e4 LT	71	attr->ia_mode &= ~S_ISGID;
	72	}
	73
	74	/* Check for setting the inode time. */
9767d749	75	if (ia_valid & (ATTR_MTIME_SET \| ATTR_ATIME_SET \| ATTR_TIMES_SET)) {
2e149670	76	if (!inode_owner_or_capable(inode))
2c27c65e	77	return -EPERM;
1da177e4	78	}
2c27c65e CH	79
2c27c65e CH	80	return 0;
1da177e4	81	}
1da177e4 LT	82	EXPORT_SYMBOL(inode_change_ok);
1da177e4 LT	83
25d9e2d1	84	/**
	85	* inode_newsize_ok - may this inode be truncated to a given size
	86	* @inode: the inode to be truncated
	87	* @offset: the new size to assign to the inode
	88	* @Returns: 0 on success, -ve errno on failure
	89	*
7bb46a67	90	* inode_newsize_ok must be called with i_mutex held.
7bb46a67	91	*
25d9e2d1	92	* inode_newsize_ok will check filesystem limits and ulimits to check that the
	93	* new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
	94	* when necessary. Caller must not proceed with inode size change if failure is
	95	* returned. @inode must be a file (not directory), with appropriate
	96	* permissions to allow truncate (inode_newsize_ok does NOT check these
	97	* conditions).
25d9e2d1	98	*/
	99	int inode_newsize_ok(const struct inode *inode, loff_t offset)
	100	{
	101	if (inode->i_size < offset) {
	102	unsigned long limit;
	103
d554ed89	104	limit = rlimit(RLIMIT_FSIZE);
25d9e2d1	105	if (limit != RLIM_INFINITY && offset > limit)
	106	goto out_sig;
	107	if (offset > inode->i_sb->s_maxbytes)
	108	goto out_big;
	109	} else {
	110	/*
	111	* truncation of in-use swapfiles is disallowed - it would
	112	* cause subsequent swapout to scribble on the now-freed
	113	* blocks.
	114	*/
	115	if (IS_SWAPFILE(inode))
	116	return -ETXTBSY;
	117	}
	118
	119	return 0;
	120	out_sig:
	121	send_sig(SIGXFSZ, current, 0);
	122	out_big:
	123	return -EFBIG;
	124	}
	125	EXPORT_SYMBOL(inode_newsize_ok);
	126
7bb46a67	127	/**
6a1a90ad	128	* setattr_copy - copy simple metadata updates into the generic inode
7bb46a67	129	* @inode: the inode to be updated
	130	* @attr: the new attributes
	131	*
6a1a90ad	132	* setattr_copy must be called with i_mutex held.
7bb46a67	133	*
6a1a90ad	134	* setattr_copy updates the inode's metadata with that specified
25985edc	135	* in attr. Noticeably missing is inode size update, which is more complex
2c27c65e	136	* as it requires pagecache updates.
7bb46a67	137	*
	138	* The inode is not marked as dirty after this operation. The rationale is
	139	* that for "simple" filesystems, the struct inode is the inode storage.
	140	* The caller is free to mark the inode dirty afterwards if needed.
	141	*/
6a1a90ad	142	void setattr_copy(struct inode inode, const struct iattr attr)
1da177e4 LT	143	{
1da177e4 LT	144	unsigned int ia_valid = attr->ia_valid;
4a30131e	145
1da177e4 LT	146	if (ia_valid & ATTR_UID)
	147	inode->i_uid = attr->ia_uid;
	148	if (ia_valid & ATTR_GID)
	149	inode->i_gid = attr->ia_gid;
	150	if (ia_valid & ATTR_ATIME)
	151	inode->i_atime = timespec_trunc(attr->ia_atime,
	152	inode->i_sb->s_time_gran);
	153	if (ia_valid & ATTR_MTIME)
	154	inode->i_mtime = timespec_trunc(attr->ia_mtime,
	155	inode->i_sb->s_time_gran);
	156	if (ia_valid & ATTR_CTIME)
	157	inode->i_ctime = timespec_trunc(attr->ia_ctime,
	158	inode->i_sb->s_time_gran);
	159	if (ia_valid & ATTR_MODE) {
	160	umode_t mode = attr->ia_mode;
	161
7fa294c8	162	if (!in_group_p(inode->i_gid) &&
23adbe12	163	!capable_wrt_inode_uidgid(inode, CAP_FSETID))
1da177e4 LT	164	mode &= ~S_ISGID;
	165	inode->i_mode = mode;
	166	}
7bb46a67	167	}
6a1a90ad	168	EXPORT_SYMBOL(setattr_copy);
7bb46a67	169
27ac0ffe BF	170	/**
	171	* notify_change - modify attributes of a filesytem object
	172	* @dentry: object affected
	173	* @iattr: new attributes
	174	* @delegated_inode: returns inode, if the inode is delegated
	175	*
	176	* The caller must hold the i_mutex on the affected object.
	177	*
	178	* If notify_change discovers a delegation in need of breaking,
	179	* it will return -EWOULDBLOCK and return a reference to the inode in
	180	* delegated_inode. The caller should then break the delegation and
	181	* retry. Because breaking a delegation may take a long time, the
	182	* caller should drop the i_mutex before doing so.
	183	*
	184	* Alternatively, a caller may pass NULL for delegated_inode. This may
	185	* be appropriate for callers that expect the underlying filesystem not
	186	* to be NFS exported. Also, passing NULL is fine for callers holding
	187	* the file open for write, as there can be no conflicting delegation in
	188	* that case.
	189	*/
	190	int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **delegated_inode)
1da177e4 LT	191	{
1da177e4 LT	192	struct inode *inode = dentry->d_inode;
8d334acd	193	umode_t mode = inode->i_mode;
1da177e4 LT	194	int error;
	195	struct timespec now;
	196	unsigned int ia_valid = attr->ia_valid;
	197
c4107b30 AM	198	WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
c4107b30 AM	199
beb29e05 MS	200	if (ia_valid & (ATTR_MODE \| ATTR_UID \| ATTR_GID \| ATTR_TIMES_SET)) {
	201	if (IS_IMMUTABLE(inode) \|\| IS_APPEND(inode))
	202	return -EPERM;
	203	}
	204
69b45732	205	if ((ia_valid & ATTR_MODE)) {
8d334acd	206	umode_t amode = attr->ia_mode;
69b45732 AK	207	/* Flag setting protected by i_mutex */
	208	if (is_sxid(amode))
	209	inode->i_flags &= ~S_NOSEC;
	210	}
	211
1da177e4 LT	212	now = current_fs_time(inode->i_sb);
	213
	214	attr->ia_ctime = now;
	215	if (!(ia_valid & ATTR_ATIME_SET))
	216	attr->ia_atime = now;
	217	if (!(ia_valid & ATTR_MTIME_SET))
	218	attr->ia_mtime = now;
b5376771 SH	219	if (ia_valid & ATTR_KILL_PRIV) {
	220	attr->ia_valid &= ~ATTR_KILL_PRIV;
	221	ia_valid &= ~ATTR_KILL_PRIV;
	222	error = security_inode_need_killpriv(dentry);
	223	if (error > 0)
	224	error = security_inode_killpriv(dentry);
	225	if (error)
	226	return error;
	227	}
6de0ec00 JL	228
	229	/*
	230	* We now pass ATTR_KILL_S*ID to the lower level setattr function so
	231	* that the function has the ability to reinterpret a mode change
	232	* that's due to these bits. This adds an implicit restriction that
	233	* no function will ever call notify_change with both ATTR_MODE and
	234	* ATTR_KILL_S*ID set.
	235	*/
	236	if ((ia_valid & (ATTR_KILL_SUID\|ATTR_KILL_SGID)) &&
	237	(ia_valid & ATTR_MODE))
	238	BUG();
	239
1da177e4	240	if (ia_valid & ATTR_KILL_SUID) {
1da177e4	241	if (mode & S_ISUID) {
6de0ec00 JL	242	ia_valid = attr->ia_valid \|= ATTR_MODE;
6de0ec00 JL	243	attr->ia_mode = (inode->i_mode & ~S_ISUID);
1da177e4 LT	244	}
	245	}
	246	if (ia_valid & ATTR_KILL_SGID) {
1da177e4 LT	247	if ((mode & (S_ISGID \| S_IXGRP)) == (S_ISGID \| S_IXGRP)) {
	248	if (!(ia_valid & ATTR_MODE)) {
	249	ia_valid = attr->ia_valid \|= ATTR_MODE;
	250	attr->ia_mode = inode->i_mode;
	251	}
	252	attr->ia_mode &= ~S_ISGID;
	253	}
	254	}
6de0ec00	255	if (!(attr->ia_valid & ~(ATTR_KILL_SUID \| ATTR_KILL_SGID)))
1da177e4 LT	256	return 0;
1da177e4 LT	257
a77b72da	258	error = security_inode_setattr(dentry, attr);
27ac0ffe BF	259	if (error)
	260	return error;
	261	error = try_break_deleg(inode, delegated_inode);
a77b72da MS	262	if (error)
	263	return error;
	264
eef2380c	265	if (inode->i_op->setattr)
a77b72da	266	error = inode->i_op->setattr(dentry, attr);
eef2380c CH	267	else
eef2380c CH	268	error = simple_setattr(dentry, attr);
1da177e4	269
975d2943	270	if (!error) {
0eeca283	271	fsnotify_change(dentry, ia_valid);
9957a504	272	ima_inode_post_setattr(dentry);
975d2943 MZ	273	evm_inode_post_setattr(dentry, ia_valid);
975d2943 MZ	274	}
0eeca283	275
1da177e4 LT	276	return error;
1da177e4 LT	277	}
1da177e4	278	EXPORT_SYMBOL(notify_change);