android_kernel_asus_sm8350/include/linux/xattr.h
Mark Salyzyn 3484eba91d FROMLIST: Add flags option to get xattr method paired to __vfs_getxattr
Add a flag option to get xattr method that could have a bit flag of
XATTR_NOSECURITY passed to it.  XATTR_NOSECURITY is generally then
set in the __vfs_getxattr path when called by security
infrastructure.

This handles the case of a union filesystem driver that is being
requested by the security layer to report back the xattr data.

For the use case where access is to be blocked by the security layer.

The path then could be security(dentry) ->
__vfs_getxattr(dentry...XATTR_NOSECURITY) ->
handler->get(dentry...XATTR_NOSECURITY) ->
__vfs_getxattr(lower_dentry...XATTR_NOSECURITY) ->
lower_handler->get(lower_dentry...XATTR_NOSECURITY)
which would report back through the chain data and success as
expected, the logging security layer at the top would have the
data to determine the access permissions and report back the target
context that was blocked.

Without the get handler flag, the path on a union filesystem would be
the errant security(dentry) -> __vfs_getxattr(dentry) ->
handler->get(dentry) -> vfs_getxattr(lower_dentry) -> nested ->
security(lower_dentry, log off) -> lower_handler->get(lower_dentry)
which would report back through the chain no data, and -EACCES.

For selinux for both cases, this would translate to a correctly
determined blocked access. In the first case with this change a correct avc
log would be reported, in the second legacy case an incorrect avc log
would be reported against an uninitialized u:object_r:unlabeled:s0
context making the logs cosmetically useless for audit2allow.

This patch series is inert and is the wide-spread addition of the
flags option for xattr functions, and a replacement of __vfs_getxattr
with __vfs_getxattr(...XATTR_NOSECURITY).

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: David Sterba <dsterba@suse.com>
Acked-by: Darrick J. Wong <darrick.wong@oracle.com>
Acked-by: Mike Marshall <hubcap@omnibond.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: linux-security-module@vger.kernel.org

(cherry picked from (rejected from archive because of too many recipients))
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 133515582
Bug: 136124883
Bug: 129319403
Change-Id: Iabbb8771939d5f66667a26bb23ddf4c562c349a1
2019-11-05 13:50:57 -08:00

113 lines
3.3 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
/*
File: linux/xattr.h
Extended attributes handling.
Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
Copyright (c) 2001-2002 Silicon Graphics, Inc. All Rights Reserved.
Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
*/
#ifndef _LINUX_XATTR_H
#define _LINUX_XATTR_H
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/spinlock.h>
#include <uapi/linux/xattr.h>
struct inode;
struct dentry;
/*
* struct xattr_handler: When @name is set, match attributes with exactly that
* name. When @prefix is set instead, match attributes with that prefix and
* with a non-empty suffix.
*/
struct xattr_handler {
const char *name;
const char *prefix;
int flags; /* fs private flags */
bool (*list)(struct dentry *dentry);
int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
struct inode *inode, const char *name, void *buffer,
size_t size, int flags);
int (*set)(const struct xattr_handler *handler, struct dentry *dentry,
struct inode *inode, const char *name, const void *buffer,
size_t size, int flags);
};
const char *xattr_full_name(const struct xattr_handler *, const char *);
struct xattr {
const char *name;
void *value;
size_t value_len;
};
ssize_t __vfs_getxattr(struct dentry *dentry, struct inode *inode,
const char *name, void *buffer, size_t size, int flags);
ssize_t vfs_getxattr(struct dentry *, const char *, void *, size_t);
ssize_t vfs_listxattr(struct dentry *d, char *list, size_t size);
int __vfs_setxattr(struct dentry *, struct inode *, const char *, const void *, size_t, int);
int __vfs_setxattr_noperm(struct dentry *, const char *, const void *, size_t, int);
int vfs_setxattr(struct dentry *, const char *, const void *, size_t, int);
int __vfs_removexattr(struct dentry *, const char *);
int vfs_removexattr(struct dentry *, const char *);
ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size);
ssize_t vfs_getxattr_alloc(struct dentry *dentry, const char *name,
char **xattr_value, size_t size, gfp_t flags);
static inline const char *xattr_prefix(const struct xattr_handler *handler)
{
return handler->prefix ?: handler->name;
}
struct simple_xattrs {
struct list_head head;
spinlock_t lock;
};
struct simple_xattr {
struct list_head list;
char *name;
size_t size;
char value[0];
};
/*
* initialize the simple_xattrs structure
*/
static inline void simple_xattrs_init(struct simple_xattrs *xattrs)
{
INIT_LIST_HEAD(&xattrs->head);
spin_lock_init(&xattrs->lock);
}
/*
* free all the xattrs
*/
static inline void simple_xattrs_free(struct simple_xattrs *xattrs)
{
struct simple_xattr *xattr, *node;
list_for_each_entry_safe(xattr, node, &xattrs->head, list) {
kfree(xattr->name);
kfree(xattr);
}
}
struct simple_xattr *simple_xattr_alloc(const void *value, size_t size);
int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
void *buffer, size_t size);
int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
const void *value, size_t size, int flags);
ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs, char *buffer,
size_t size);
void simple_xattr_list_add(struct simple_xattrs *xattrs,
struct simple_xattr *new_xattr);
#endif /* _LINUX_XATTR_H */