fs/posix_acl.c - maze/linux - Git at Google

 /*
  * linux/fs/posix_acl.c
  *
  *  Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  *
  *  Fixes from William Schumacher incorporated on 15 March 2001.
  *     (Reported by Charles Bertsch, <CBertsch@microtest.com>).
  */

 /*
  *  This file contains generic functions for manipulating
  *  POSIX 1003.1e draft standard 17 ACLs.
  */

 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <asm/atomic.h>
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/posix_acl.h>
 #include <linux/module.h>

 #include <linux/errno.h>

 EXPORT_SYMBOL(posix_acl_alloc);
 EXPORT_SYMBOL(posix_acl_clone);
 EXPORT_SYMBOL(posix_acl_valid);
 EXPORT_SYMBOL(posix_acl_equiv_mode);
 EXPORT_SYMBOL(posix_acl_from_mode);
 EXPORT_SYMBOL(posix_acl_create_masq);
 EXPORT_SYMBOL(posix_acl_chmod_masq);
 EXPORT_SYMBOL(posix_acl_permission);

 /*
  * Allocate a new ACL with the specified number of entries.
  */
 struct posix_acl *
 posix_acl_alloc(int count, int flags)
 {
 	const size_t size = sizeof(struct posix_acl) +
 	                    count * sizeof(struct posix_acl_entry);
 	struct posix_acl *acl = kmalloc(size, flags);
 	if (acl) {
 		atomic_set(&acl->a_refcount, 1);
 		acl->a_count = count;
 	}
 	return acl;
 }

 /*
  * Clone an ACL.
  */
 struct posix_acl *
 posix_acl_clone(const struct posix_acl *acl, int flags)
 {
 	struct posix_acl *clone = NULL;

 	if (acl) {
 		int size = sizeof(struct posix_acl) + acl->a_count *
 		           sizeof(struct posix_acl_entry);
 		clone = kmalloc(size, flags);
 		if (clone) {
 			memcpy(clone, acl, size);
 			atomic_set(&clone->a_refcount, 1);
 		}
 	}
 	return clone;
 }

 /*
  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
  */
 int
 posix_acl_valid(const struct posix_acl *acl)
 {
 	const struct posix_acl_entry *pa, *pe;
 	int state = ACL_USER_OBJ;
 	unsigned int id = 0;  /* keep gcc happy */
 	int needs_mask = 0;

 	FOREACH_ACL_ENTRY(pa, acl, pe) {
 		if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
 			return -EINVAL;
 		switch (pa->e_tag) {
 			case ACL_USER_OBJ:
 				if (state == ACL_USER_OBJ) {
 					id = 0;
 					state = ACL_USER;
 					break;
 				}
 				return -EINVAL;

 			case ACL_USER:
 				if (state != ACL_USER)
 					return -EINVAL;
 				if (pa->e_id == ACL_UNDEFINED_ID ||
 				    pa->e_id < id)
 					return -EINVAL;
 				id = pa->e_id + 1;
 				needs_mask = 1;
 				break;

 			case ACL_GROUP_OBJ:
 				if (state == ACL_USER) {
 					id = 0;
 					state = ACL_GROUP;
 					break;
 				}
 				return -EINVAL;

 			case ACL_GROUP:
 				if (state != ACL_GROUP)
 					return -EINVAL;
 				if (pa->e_id == ACL_UNDEFINED_ID ||
 				    pa->e_id < id)
 					return -EINVAL;
 				id = pa->e_id + 1;
 				needs_mask = 1;
 				break;

 			case ACL_MASK:
 				if (state != ACL_GROUP)
 					return -EINVAL;
 				state = ACL_OTHER;
 				break;

 			case ACL_OTHER:
 				if (state == ACL_OTHER ||
 				    (state == ACL_GROUP && !needs_mask)) {
 					state = 0;
 					break;
 				}
 				return -EINVAL;

 			default:
 				return -EINVAL;
 		}
 	}
 	if (state == 0)
 		return 0;
 	return -EINVAL;
 }

 /*
  * Returns 0 if the acl can be exactly represented in the traditional
  * file mode permission bits, or else 1. Returns -E... on error.
  */
 int
 posix_acl_equiv_mode(const struct posix_acl *acl, mode_t *mode_p)
 {
 	const struct posix_acl_entry *pa, *pe;
 	mode_t mode = 0;
 	int not_equiv = 0;

 	FOREACH_ACL_ENTRY(pa, acl, pe) {
 		switch (pa->e_tag) {
 			case ACL_USER_OBJ:
 				mode |= (pa->e_perm & S_IRWXO) << 6;
 				break;
 			case ACL_GROUP_OBJ:
 				mode |= (pa->e_perm & S_IRWXO) << 3;
 				break;
 			case ACL_OTHER:
 				mode |= pa->e_perm & S_IRWXO;
 				break;
 			case ACL_MASK:
 				mode = (mode & ~S_IRWXG) |
 				       ((pa->e_perm & S_IRWXO) << 3);
 				not_equiv = 1;
 				break;
 			case ACL_USER:
 			case ACL_GROUP:
 				not_equiv = 1;
 				break;
 			default:
 				return -EINVAL;
 		}
 	}
         if (mode_p)
                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
         return not_equiv;
 }

 /*
  * Create an ACL representing the file mode permission bits of an inode.
  */
 struct posix_acl *
 posix_acl_from_mode(mode_t mode, int flags)
 {
 	struct posix_acl *acl = posix_acl_alloc(3, flags);
 	if (!acl)
 		return ERR_PTR(-ENOMEM);

 	acl->a_entries[0].e_tag  = ACL_USER_OBJ;
 	acl->a_entries[0].e_id   = ACL_UNDEFINED_ID;
 	acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;

 	acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
 	acl->a_entries[1].e_id   = ACL_UNDEFINED_ID;
 	acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;

 	acl->a_entries[2].e_tag  = ACL_OTHER;
 	acl->a_entries[2].e_id   = ACL_UNDEFINED_ID;
 	acl->a_entries[2].e_perm = (mode & S_IRWXO);
 	return acl;
 }

 /*
  * Return 0 if current is granted want access to the inode
  * by the acl. Returns -E... otherwise.
  */
 int
 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
 {
 	const struct posix_acl_entry *pa, *pe, *mask_obj;
 	int found = 0;

 	FOREACH_ACL_ENTRY(pa, acl, pe) {
                 switch(pa->e_tag) {
                         case ACL_USER_OBJ:
 				/* (May have been checked already) */
                                 if (inode->i_uid == current->fsuid)
                                         goto check_perm;
                                 break;
                         case ACL_USER:
                                 if (pa->e_id == current->fsuid)
                                         goto mask;
 				break;
                         case ACL_GROUP_OBJ:
                                 if (in_group_p(inode->i_gid)) {
 					found = 1;
 					if ((pa->e_perm & want) == want)
 						goto mask;
                                 }
 				break;
                         case ACL_GROUP:
                                 if (in_group_p(pa->e_id)) {
 					found = 1;
 					if ((pa->e_perm & want) == want)
 						goto mask;
                                 }
                                 break;
                         case ACL_MASK:
                                 break;
                         case ACL_OTHER:
 				if (found)
 					return -EACCES;
 				else
 					goto check_perm;
 			default:
 				return -EIO;
                 }
         }
 	return -EIO;

 mask:
 	for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
 		if (mask_obj->e_tag == ACL_MASK) {
 			if ((pa->e_perm & mask_obj->e_perm & want) == want)
 				return 0;
 			return -EACCES;
 		}
 	}

 check_perm:
 	if ((pa->e_perm & want) == want)
 		return 0;
 	return -EACCES;
 }

 /*
  * Modify acl when creating a new inode. The caller must ensure the acl is
  * only referenced once.
  *
  * mode_p initially must contain the mode parameter to the open() / creat()
  * system calls. All permissions that are not granted by the acl are removed.
  * The permissions in the acl are changed to reflect the mode_p parameter.
  */
 int
 posix_acl_create_masq(struct posix_acl *acl, mode_t *mode_p)
 {
 	struct posix_acl_entry *pa, *pe;
 	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 	mode_t mode = *mode_p;
 	int not_equiv = 0;

 	/* assert(atomic_read(acl->a_refcount) == 1); */

 	FOREACH_ACL_ENTRY(pa, acl, pe) {
                 switch(pa->e_tag) {
                         case ACL_USER_OBJ:
 				pa->e_perm &= (mode >> 6) | ~S_IRWXO;
 				mode &= (pa->e_perm << 6) | ~S_IRWXU;
 				break;

 			case ACL_USER:
 			case ACL_GROUP:
 				not_equiv = 1;
 				break;

                         case ACL_GROUP_OBJ:
 				group_obj = pa;
                                 break;

                         case ACL_OTHER:
 				pa->e_perm &= mode | ~S_IRWXO;
 				mode &= pa->e_perm | ~S_IRWXO;
                                 break;

                         case ACL_MASK:
 				mask_obj = pa;
 				not_equiv = 1;
                                 break;

 			default:
 				return -EIO;
                 }
         }

 	if (mask_obj) {
 		mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 		mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
 	} else {
 		if (!group_obj)
 			return -EIO;
 		group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
 		mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
 	}

 	*mode_p = (*mode_p & ~S_IRWXUGO) | mode;
         return not_equiv;
 }

 /*
  * Modify the ACL for the chmod syscall.
  */
 int
 posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
 {
 	struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
 	struct posix_acl_entry *pa, *pe;

 	/* assert(atomic_read(acl->a_refcount) == 1); */

 	FOREACH_ACL_ENTRY(pa, acl, pe) {
 		switch(pa->e_tag) {
 			case ACL_USER_OBJ:
 				pa->e_perm = (mode & S_IRWXU) >> 6;
 				break;

 			case ACL_USER:
 			case ACL_GROUP:
 				break;

 			case ACL_GROUP_OBJ:
 				group_obj = pa;
 				break;

 			case ACL_MASK:
 				mask_obj = pa;
 				break;

 			case ACL_OTHER:
 				pa->e_perm = (mode & S_IRWXO);
 				break;

 			default:
 				return -EIO;
 		}
 	}

 	if (mask_obj) {
 		mask_obj->e_perm = (mode & S_IRWXG) >> 3;
 	} else {
 		if (!group_obj)
 			return -EIO;
 		group_obj->e_perm = (mode & S_IRWXG) >> 3;
 	}

 	return 0;
 }
	/*
	* linux/fs/posix_acl.c
	*
	* Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
	*
	* Fixes from William Schumacher incorporated on 15 March 2001.
	* (Reported by Charles Bertsch, <CBertsch@microtest.com>).
	*/

	/*
	* This file contains generic functions for manipulating
	* POSIX 1003.1e draft standard 17 ACLs.
	*/

	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <asm/atomic.h>
	#include <linux/fs.h>
	#include <linux/sched.h>
	#include <linux/posix_acl.h>
	#include <linux/module.h>

	#include <linux/errno.h>

	EXPORT_SYMBOL(posix_acl_alloc);
	EXPORT_SYMBOL(posix_acl_clone);
	EXPORT_SYMBOL(posix_acl_valid);
	EXPORT_SYMBOL(posix_acl_equiv_mode);
	EXPORT_SYMBOL(posix_acl_from_mode);
	EXPORT_SYMBOL(posix_acl_create_masq);
	EXPORT_SYMBOL(posix_acl_chmod_masq);
	EXPORT_SYMBOL(posix_acl_permission);

	/*
	* Allocate a new ACL with the specified number of entries.
	*/
	struct posix_acl *
	posix_acl_alloc(int count, int flags)
	{
	const size_t size = sizeof(struct posix_acl) +
	count * sizeof(struct posix_acl_entry);
	struct posix_acl *acl = kmalloc(size, flags);
	if (acl) {
	atomic_set(&acl->a_refcount, 1);
	acl->a_count = count;
	}
	return acl;
	}

	/*
	* Clone an ACL.
	*/
	struct posix_acl *
	posix_acl_clone(const struct posix_acl *acl, int flags)
	{
	struct posix_acl *clone = NULL;

	if (acl) {
	int size = sizeof(struct posix_acl) + acl->a_count *
	sizeof(struct posix_acl_entry);
	clone = kmalloc(size, flags);
	if (clone) {
	memcpy(clone, acl, size);
	atomic_set(&clone->a_refcount, 1);
	}
	}
	return clone;
	}

	/*
	* Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
	*/
	int
	posix_acl_valid(const struct posix_acl *acl)
	{
	const struct posix_acl_entry pa, pe;
	int state = ACL_USER_OBJ;
	unsigned int id = 0; /* keep gcc happy */
	int needs_mask = 0;

	FOREACH_ACL_ENTRY(pa, acl, pe) {
	if (pa->e_perm & ~(ACL_READ\|ACL_WRITE\|ACL_EXECUTE))
	return -EINVAL;
	switch (pa->e_tag) {
	case ACL_USER_OBJ:
	if (state == ACL_USER_OBJ) {
	id = 0;
	state = ACL_USER;
	break;
	}
	return -EINVAL;

	case ACL_USER:
	if (state != ACL_USER)
	return -EINVAL;
	if (pa->e_id == ACL_UNDEFINED_ID \|\|
	pa->e_id < id)
	return -EINVAL;
	id = pa->e_id + 1;
	needs_mask = 1;
	break;

	case ACL_GROUP_OBJ:
	if (state == ACL_USER) {
	id = 0;
	state = ACL_GROUP;
	break;
	}
	return -EINVAL;

	case ACL_GROUP:
	if (state != ACL_GROUP)
	return -EINVAL;
	if (pa->e_id == ACL_UNDEFINED_ID \|\|
	pa->e_id < id)
	return -EINVAL;
	id = pa->e_id + 1;
	needs_mask = 1;
	break;

	case ACL_MASK:
	if (state != ACL_GROUP)
	return -EINVAL;
	state = ACL_OTHER;
	break;

	case ACL_OTHER:
	if (state == ACL_OTHER \|\|
	(state == ACL_GROUP && !needs_mask)) {
	state = 0;
	break;
	}
	return -EINVAL;

	default:
	return -EINVAL;
	}
	}
	if (state == 0)
	return 0;
	return -EINVAL;
	}

	/*
	* Returns 0 if the acl can be exactly represented in the traditional
	* file mode permission bits, or else 1. Returns -E... on error.
	*/
	int
	posix_acl_equiv_mode(const struct posix_acl acl, mode_t mode_p)
	{
	const struct posix_acl_entry pa, pe;
	mode_t mode = 0;
	int not_equiv = 0;

	FOREACH_ACL_ENTRY(pa, acl, pe) {
	switch (pa->e_tag) {
	case ACL_USER_OBJ:
	mode \|= (pa->e_perm & S_IRWXO) << 6;
	break;
	case ACL_GROUP_OBJ:
	mode \|= (pa->e_perm & S_IRWXO) << 3;
	break;
	case ACL_OTHER:
	mode \|= pa->e_perm & S_IRWXO;
	break;
	case ACL_MASK:
	mode = (mode & ~S_IRWXG) \|
	((pa->e_perm & S_IRWXO) << 3);
	not_equiv = 1;
	break;
	case ACL_USER:
	case ACL_GROUP:
	not_equiv = 1;
	break;
	default:
	return -EINVAL;
	}
	}
	if (mode_p)
	mode_p = (mode_p & ~S_IRWXUGO) \| mode;
	return not_equiv;
	}

	/*
	* Create an ACL representing the file mode permission bits of an inode.
	*/
	struct posix_acl *
	posix_acl_from_mode(mode_t mode, int flags)
	{
	struct posix_acl *acl = posix_acl_alloc(3, flags);
	if (!acl)
	return ERR_PTR(-ENOMEM);

	acl->a_entries[0].e_tag = ACL_USER_OBJ;
	acl->a_entries[0].e_id = ACL_UNDEFINED_ID;
	acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;

	acl->a_entries[1].e_tag = ACL_GROUP_OBJ;
	acl->a_entries[1].e_id = ACL_UNDEFINED_ID;
	acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;

	acl->a_entries[2].e_tag = ACL_OTHER;
	acl->a_entries[2].e_id = ACL_UNDEFINED_ID;
	acl->a_entries[2].e_perm = (mode & S_IRWXO);
	return acl;
	}

	/*
	* Return 0 if current is granted want access to the inode
	* by the acl. Returns -E... otherwise.
	*/
	int
	posix_acl_permission(struct inode inode, const struct posix_acl acl, int want)
	{
	const struct posix_acl_entry pa, pe, *mask_obj;
	int found = 0;

	FOREACH_ACL_ENTRY(pa, acl, pe) {
	switch(pa->e_tag) {
	case ACL_USER_OBJ:
	/* (May have been checked already) */
	if (inode->i_uid == current->fsuid)
	goto check_perm;
	break;
	case ACL_USER:
	if (pa->e_id == current->fsuid)
	goto mask;
	break;
	case ACL_GROUP_OBJ:
	if (in_group_p(inode->i_gid)) {
	found = 1;
	if ((pa->e_perm & want) == want)
	goto mask;
	}
	break;
	case ACL_GROUP:
	if (in_group_p(pa->e_id)) {
	found = 1;
	if ((pa->e_perm & want) == want)
	goto mask;
	}
	break;
	case ACL_MASK:
	break;
	case ACL_OTHER:
	if (found)
	return -EACCES;
	else
	goto check_perm;
	default:
	return -EIO;
	}
	}
	return -EIO;

	mask:
	for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
	if (mask_obj->e_tag == ACL_MASK) {
	if ((pa->e_perm & mask_obj->e_perm & want) == want)
	return 0;
	return -EACCES;
	}
	}

	check_perm:
	if ((pa->e_perm & want) == want)
	return 0;
	return -EACCES;
	}

	/*
	* Modify acl when creating a new inode. The caller must ensure the acl is
	* only referenced once.
	*
	* mode_p initially must contain the mode parameter to the open() / creat()
	* system calls. All permissions that are not granted by the acl are removed.
	* The permissions in the acl are changed to reflect the mode_p parameter.
	*/
	int
	posix_acl_create_masq(struct posix_acl acl, mode_t mode_p)
	{
	struct posix_acl_entry pa, pe;
	struct posix_acl_entry group_obj = NULL, mask_obj = NULL;
	mode_t mode = *mode_p;
	int not_equiv = 0;

	/* assert(atomic_read(acl->a_refcount) == 1); */

	FOREACH_ACL_ENTRY(pa, acl, pe) {
	switch(pa->e_tag) {
	case ACL_USER_OBJ:
	pa->e_perm &= (mode >> 6) \| ~S_IRWXO;
	mode &= (pa->e_perm << 6) \| ~S_IRWXU;
	break;

	case ACL_USER:
	case ACL_GROUP:
	not_equiv = 1;
	break;

	case ACL_GROUP_OBJ:
	group_obj = pa;
	break;

	case ACL_OTHER:
	pa->e_perm &= mode \| ~S_IRWXO;
	mode &= pa->e_perm \| ~S_IRWXO;
	break;

	case ACL_MASK:
	mask_obj = pa;
	not_equiv = 1;
	break;

	default:
	return -EIO;
	}
	}

	if (mask_obj) {
	mask_obj->e_perm &= (mode >> 3) \| ~S_IRWXO;
	mode &= (mask_obj->e_perm << 3) \| ~S_IRWXG;
	} else {
	if (!group_obj)
	return -EIO;
	group_obj->e_perm &= (mode >> 3) \| ~S_IRWXO;
	mode &= (group_obj->e_perm << 3) \| ~S_IRWXG;
	}

	mode_p = (mode_p & ~S_IRWXUGO) \| mode;
	return not_equiv;
	}

	/*
	* Modify the ACL for the chmod syscall.
	*/
	int
	posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
	{
	struct posix_acl_entry group_obj = NULL, mask_obj = NULL;
	struct posix_acl_entry pa, pe;

	/* assert(atomic_read(acl->a_refcount) == 1); */

	FOREACH_ACL_ENTRY(pa, acl, pe) {
	switch(pa->e_tag) {
	case ACL_USER_OBJ:
	pa->e_perm = (mode & S_IRWXU) >> 6;
	break;

	case ACL_USER:
	case ACL_GROUP:
	break;

	case ACL_GROUP_OBJ:
	group_obj = pa;
	break;

	case ACL_MASK:
	mask_obj = pa;
	break;

	case ACL_OTHER:
	pa->e_perm = (mode & S_IRWXO);
	break;

	default:
	return -EIO;
	}
	}

	if (mask_obj) {
	mask_obj->e_perm = (mode & S_IRWXG) >> 3;
	} else {
	if (!group_obj)
	return -EIO;
	group_obj->e_perm = (mode & S_IRWXG) >> 3;
	}

	return 0;
	}