acl.c

基于组件方式开发操作系统的OSKIT源代码

/*
 *  linux/fs/ufs/acl.c
 *
 * Copyright (C) 1998
 * Daniel Pirkl <[e-mail]>
 * Charles University, Faculty of Mathematics and Physics
 *
 *  from
 *
 *  linux/fs/ext2/acl.c
 *
 * Copyright (C) 1993, 1994, 1995
 * Remy Card ([e-mail])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 */

/*
 * This file will contain the Access Control Lists management for UFS
 */

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/ufs_fs.h>
#include <linux/sched.h>
#include <linux/stat.h>

/*
 * ufs_permission ()
 *
 * Check for access rights
 */
int ufs_permission (struct inode * inode, int mask)
{
	unsigned short mode = inode->i_mode;

	/*
	 * Nobody gets write access to a file on a readonly-fs
	 */
	if ((mask & S_IWOTH) && 
	    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)) &&
	    IS_RDONLY(inode))
		return -EROFS;
	/*
	 * Nobody gets write access to an immutable file
	 */
	if ((mask & S_IWOTH) && IS_IMMUTABLE(inode))
		return -EACCES;

	/*
	 * If no ACL, checks using the file mode
	 */
	else if (current->fsuid == inode->i_uid)
		mode >>= 6;
	else if (in_group_p (inode->i_gid))
		mode >>= 3;
	/*
	 * Access is always granted for root. We now check last,
	 * though, for BSD process accounting correctness
	 */
	if (((mode & mask & S_IRWXO) == mask) || capable(CAP_DAC_OVERRIDE))
		return 0;
	if ((mask == S_IROTH) ||
	    (S_ISDIR(mode)  && !(mask & ~(S_IROTH | S_IXOTH))))
		if (capable(CAP_DAC_READ_SEARCH))
			return 0;
	return -EACCES;
}