/* *  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)) &&	    !inode_capable(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))) &&	    !inode_capable(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) &&		    !inode_capable(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) &&		    !inode_capable(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_SIZE) && IS_I_VERSION(inode)) {		if (attr->ia_size != inode->i_size)			inode_inc_iversion(inode);	} 	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);