254947d479
Implement code to derive a new set of creds for the cachefiles to use when making VFS or I/O calls and to change the auditing info since the application interacting with the network filesystem is not accessing the cache directly. Cachefiles uses override_creds() to change the effective creds temporarily. set_security_override_from_ctx() is called to derive the LSM 'label' that the cachefiles driver will act with. set_create_files_as() is called to determine the LSM 'label' that will be applied to files and directories created in the cache. These functions alter the new creds. Also implement a couple of functions to wrap the calls to begin/end cred overriding. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/163819627469.215744.3603633690679962985.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906928172.143852.15886637013364286786.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967138138.1823006.7620933448261939504.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021537001.640689.4081334436031700558.stgit@warthog.procyon.org.uk/ # v4
113 lines
2.5 KiB
C
113 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/* CacheFiles security management
|
|
*
|
|
* Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
|
|
* Written by David Howells (dhowells@redhat.com)
|
|
*/
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/cred.h>
|
|
#include "internal.h"
|
|
|
|
/*
|
|
* determine the security context within which we access the cache from within
|
|
* the kernel
|
|
*/
|
|
int cachefiles_get_security_ID(struct cachefiles_cache *cache)
|
|
{
|
|
struct cred *new;
|
|
int ret;
|
|
|
|
_enter("{%s}", cache->secctx);
|
|
|
|
new = prepare_kernel_cred(current);
|
|
if (!new) {
|
|
ret = -ENOMEM;
|
|
goto error;
|
|
}
|
|
|
|
if (cache->secctx) {
|
|
ret = set_security_override_from_ctx(new, cache->secctx);
|
|
if (ret < 0) {
|
|
put_cred(new);
|
|
pr_err("Security denies permission to nominate security context: error %d\n",
|
|
ret);
|
|
goto error;
|
|
}
|
|
}
|
|
|
|
cache->cache_cred = new;
|
|
ret = 0;
|
|
error:
|
|
_leave(" = %d", ret);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* see if mkdir and create can be performed in the root directory
|
|
*/
|
|
static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
|
|
struct dentry *root)
|
|
{
|
|
int ret;
|
|
|
|
ret = security_inode_mkdir(d_backing_inode(root), root, 0);
|
|
if (ret < 0) {
|
|
pr_err("Security denies permission to make dirs: error %d",
|
|
ret);
|
|
return ret;
|
|
}
|
|
|
|
ret = security_inode_create(d_backing_inode(root), root, 0);
|
|
if (ret < 0)
|
|
pr_err("Security denies permission to create files: error %d",
|
|
ret);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* check the security details of the on-disk cache
|
|
* - must be called with security override in force
|
|
* - must return with a security override in force - even in the case of an
|
|
* error
|
|
*/
|
|
int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
|
|
struct dentry *root,
|
|
const struct cred **_saved_cred)
|
|
{
|
|
struct cred *new;
|
|
int ret;
|
|
|
|
_enter("");
|
|
|
|
/* duplicate the cache creds for COW (the override is currently in
|
|
* force, so we can use prepare_creds() to do this) */
|
|
new = prepare_creds();
|
|
if (!new)
|
|
return -ENOMEM;
|
|
|
|
cachefiles_end_secure(cache, *_saved_cred);
|
|
|
|
/* use the cache root dir's security context as the basis with
|
|
* which create files */
|
|
ret = set_create_files_as(new, d_backing_inode(root));
|
|
if (ret < 0) {
|
|
abort_creds(new);
|
|
cachefiles_begin_secure(cache, _saved_cred);
|
|
_leave(" = %d [cfa]", ret);
|
|
return ret;
|
|
}
|
|
|
|
put_cred(cache->cache_cred);
|
|
cache->cache_cred = new;
|
|
|
|
cachefiles_begin_secure(cache, _saved_cred);
|
|
ret = cachefiles_check_cache_dir(cache, root);
|
|
|
|
if (ret == -EOPNOTSUPP)
|
|
ret = 0;
|
|
_leave(" = %d", ret);
|
|
return ret;
|
|
}
|