linux/fs/ext2/acl.c
Ernesto A. Fernández fe26569eb9 ext2: preserve i_mode if ext2_set_acl() fails
When changing a file's acl mask, ext2_set_acl() will first set the group
bits of i_mode to the value of the mask, and only then set the actual
extended attribute representing the new acl.

If the second part fails (due to lack of space, for example) and the file
had no acl attribute to begin with, the system will from now on assume
that the mask permission bits are actual group permission bits, potentially
granting access to the wrong users.

Prevent this by only changing the inode mode after the acl has been set.

[JK: Rebased on top of "ext2: Don't clear SGID when inheriting ACLs"]
Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
2017-07-18 11:23:56 +02:00

266 lines
5.7 KiB
C

/*
* linux/fs/ext2/acl.c
*
* Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
*/
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include "ext2.h"
#include "xattr.h"
#include "acl.h"
/*
* Convert from filesystem to in-memory representation.
*/
static struct posix_acl *
ext2_acl_from_disk(const void *value, size_t size)
{
const char *end = (char *)value + size;
int n, count;
struct posix_acl *acl;
if (!value)
return NULL;
if (size < sizeof(ext2_acl_header))
return ERR_PTR(-EINVAL);
if (((ext2_acl_header *)value)->a_version !=
cpu_to_le32(EXT2_ACL_VERSION))
return ERR_PTR(-EINVAL);
value = (char *)value + sizeof(ext2_acl_header);
count = ext2_acl_count(size);
if (count < 0)
return ERR_PTR(-EINVAL);
if (count == 0)
return NULL;
acl = posix_acl_alloc(count, GFP_KERNEL);
if (!acl)
return ERR_PTR(-ENOMEM);
for (n=0; n < count; n++) {
ext2_acl_entry *entry =
(ext2_acl_entry *)value;
if ((char *)value + sizeof(ext2_acl_entry_short) > end)
goto fail;
acl->a_entries[n].e_tag = le16_to_cpu(entry->e_tag);
acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
switch(acl->a_entries[n].e_tag) {
case ACL_USER_OBJ:
case ACL_GROUP_OBJ:
case ACL_MASK:
case ACL_OTHER:
value = (char *)value +
sizeof(ext2_acl_entry_short);
break;
case ACL_USER:
value = (char *)value + sizeof(ext2_acl_entry);
if ((char *)value > end)
goto fail;
acl->a_entries[n].e_uid =
make_kuid(&init_user_ns,
le32_to_cpu(entry->e_id));
break;
case ACL_GROUP:
value = (char *)value + sizeof(ext2_acl_entry);
if ((char *)value > end)
goto fail;
acl->a_entries[n].e_gid =
make_kgid(&init_user_ns,
le32_to_cpu(entry->e_id));
break;
default:
goto fail;
}
}
if (value != end)
goto fail;
return acl;
fail:
posix_acl_release(acl);
return ERR_PTR(-EINVAL);
}
/*
* Convert from in-memory to filesystem representation.
*/
static void *
ext2_acl_to_disk(const struct posix_acl *acl, size_t *size)
{
ext2_acl_header *ext_acl;
char *e;
size_t n;
*size = ext2_acl_size(acl->a_count);
ext_acl = kmalloc(sizeof(ext2_acl_header) + acl->a_count *
sizeof(ext2_acl_entry), GFP_KERNEL);
if (!ext_acl)
return ERR_PTR(-ENOMEM);
ext_acl->a_version = cpu_to_le32(EXT2_ACL_VERSION);
e = (char *)ext_acl + sizeof(ext2_acl_header);
for (n=0; n < acl->a_count; n++) {
const struct posix_acl_entry *acl_e = &acl->a_entries[n];
ext2_acl_entry *entry = (ext2_acl_entry *)e;
entry->e_tag = cpu_to_le16(acl_e->e_tag);
entry->e_perm = cpu_to_le16(acl_e->e_perm);
switch(acl_e->e_tag) {
case ACL_USER:
entry->e_id = cpu_to_le32(
from_kuid(&init_user_ns, acl_e->e_uid));
e += sizeof(ext2_acl_entry);
break;
case ACL_GROUP:
entry->e_id = cpu_to_le32(
from_kgid(&init_user_ns, acl_e->e_gid));
e += sizeof(ext2_acl_entry);
break;
case ACL_USER_OBJ:
case ACL_GROUP_OBJ:
case ACL_MASK:
case ACL_OTHER:
e += sizeof(ext2_acl_entry_short);
break;
default:
goto fail;
}
}
return (char *)ext_acl;
fail:
kfree(ext_acl);
return ERR_PTR(-EINVAL);
}
/*
* inode->i_mutex: don't care
*/
struct posix_acl *
ext2_get_acl(struct inode *inode, int type)
{
int name_index;
char *value = NULL;
struct posix_acl *acl;
int retval;
switch (type) {
case ACL_TYPE_ACCESS:
name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
break;
case ACL_TYPE_DEFAULT:
name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
break;
default:
BUG();
}
retval = ext2_xattr_get(inode, name_index, "", NULL, 0);
if (retval > 0) {
value = kmalloc(retval, GFP_KERNEL);
if (!value)
return ERR_PTR(-ENOMEM);
retval = ext2_xattr_get(inode, name_index, "", value, retval);
}
if (retval > 0)
acl = ext2_acl_from_disk(value, retval);
else if (retval == -ENODATA || retval == -ENOSYS)
acl = NULL;
else
acl = ERR_PTR(retval);
kfree(value);
return acl;
}
static int
__ext2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
{
int name_index;
void *value = NULL;
size_t size = 0;
int error;
switch(type) {
case ACL_TYPE_ACCESS:
name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
break;
case ACL_TYPE_DEFAULT:
name_index = EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT;
if (!S_ISDIR(inode->i_mode))
return acl ? -EACCES : 0;
break;
default:
return -EINVAL;
}
if (acl) {
value = ext2_acl_to_disk(acl, &size);
if (IS_ERR(value))
return (int)PTR_ERR(value);
}
error = ext2_xattr_set(inode, name_index, "", value, size, 0);
kfree(value);
if (!error)
set_cached_acl(inode, type, acl);
return error;
}
/*
* inode->i_mutex: down
*/
int
ext2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
{
int error;
int update_mode = 0;
umode_t mode = inode->i_mode;
if (type == ACL_TYPE_ACCESS && acl) {
error = posix_acl_update_mode(inode, &mode, &acl);
if (error)
return error;
update_mode = 1;
}
error = __ext2_set_acl(inode, acl, type);
if (!error && update_mode) {
inode->i_mode = mode;
inode->i_ctime = current_time(inode);
mark_inode_dirty(inode);
}
return error;
}
/*
* Initialize the ACLs of a new inode. Called from ext2_new_inode.
*
* dir->i_mutex: down
* inode->i_mutex: up (access to inode is still exclusive)
*/
int
ext2_init_acl(struct inode *inode, struct inode *dir)
{
struct posix_acl *default_acl, *acl;
int error;
error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
if (error)
return error;
if (default_acl) {
error = __ext2_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
posix_acl_release(default_acl);
}
if (acl) {
if (!error)
error = __ext2_set_acl(inode, acl, ACL_TYPE_ACCESS);
posix_acl_release(acl);
}
return error;
}