attr.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 104 行

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

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/string.h>

/* Taken over from the old code... */

/* POSIX UID/GID verification for setting inode attributes. */
int inode_change_ok(struct inode *inode, struct iattr *attr)
{
	int retval = -EPERM;
	unsigned int ia_valid = attr->ia_valid;

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

	/* Make sure a caller can chown. */
	if ((ia_valid & ATTR_UID) &&
	    (current->fsuid != inode->i_uid ||
	     attr->ia_uid != inode->i_uid) && !capable(CAP_CHOWN))
		goto error;

	/* Make sure caller can chgrp. */
	if ((ia_valid & ATTR_GID) &&
	    (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid) &&
	    !capable(CAP_CHOWN))
		goto error;

	/* Make sure a caller can chmod. */
	if (ia_valid & ATTR_MODE) {
		if ((current->fsuid != inode->i_uid) && !capable(CAP_FOWNER))
			goto error;
		/* Also check the setgid bit! */
		if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
				inode->i_gid) && !capable(CAP_FSETID))
			attr->ia_mode &= ~S_ISGID;
	}

	/* Check for setting the inode time. */
	if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
		if (current->fsuid != inode->i_uid && !capable(CAP_FOWNER))
			goto error;
	}
fine:
	retval = 0;
error:
	return retval;
}

void inode_setattr(struct inode * inode, 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_SIZE)
		inode->i_size = attr->ia_size;
	if (ia_valid & ATTR_ATIME)
		inode->i_atime = attr->ia_atime;
	if (ia_valid & ATTR_MTIME)
		inode->i_mtime = attr->ia_mtime;
	if (ia_valid & ATTR_CTIME)
		inode->i_ctime = attr->ia_ctime;
	if (ia_valid & ATTR_MODE) {
		inode->i_mode = attr->ia_mode;
		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
			inode->i_mode &= ~S_ISGID;
	}
	mark_inode_dirty(inode);
}

int notify_change(struct dentry * dentry, struct iattr * attr)
{
	struct inode *inode = dentry->d_inode;
	int error;
	time_t now = CURRENT_TIME;
	unsigned int ia_valid = attr->ia_valid;

	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 (inode->i_sb && inode->i_sb->s_op &&
	    inode->i_sb->s_op->notify_change) 
		error = inode->i_sb->s_op->notify_change(dentry, attr);
	else {
		error = inode_change_ok(inode, attr);
		if (!error)
			inode_setattr(inode, attr);
	}
	return error;
}