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### Background Various admin operations will be invoked by some userspace task, but the work will be done on a separate kernel thread at a later time. Snapshots are an example, which are triggered through zfs_ioc_snapshot() -> dsl_dataset_snapshot(), but the actual work is from a task dispatched to dp_sync_taskq. Many such tasks end up in dsl_enforce_ds_ss_limits(), where various limits and permissions are enforced. Among other things, it is necessary to ensure that the invoking task (that is, the user) has permission to do things. We can't simply check if the running task has permission; it is a privileged kernel thread, which can do anything. However, in the general case it's not safe to simply query the task for its permissions at the check time, as the task may not exist any more, or its permissions may have changed since it was first invoked. So instead, we capture the permissions by saving CRED() in the user task, and then using it for the check through the secpolicy_* functions. ### Current implementation The current code calls CRED() to get the credential, which gets a pointer to the cred_t inside the current task and passes it to the worker task. However, it doesn't take a reference to the cred_t, and so expects that it won't change, and that the task continues to exist. In practice that is always the case, because we don't let the calling task return from the kernel until the work is done. For Linux, we also take a reference to the current task, because the Linux credential APIs for the most part do not check an arbitrary credential, but rather, query what a task can do. See secpolicy_zfs_proc(). Again, we don't take a reference on the task, just a pointer to it. ### Changes We change to calling crhold() on the task credential, and crfree() when we're done with it. This ensures it stays alive and unchanged for the duration of the call. On the Linux side, we change the main policy checking function priv_policy_ns() to use override_creds()/revert_creds() if necessary to make the provided credential active in the current task, allowing the standard task-permission APIs to do the needed check. Since the task pointer is no longer required, this lets us entirely remove secpolicy_zfs_proc() and the need to carry a task pointer around as well. Sponsored-by: https://despairlabs.com/sponsor/ Signed-off-by: Rob Norris <robn@despairlabs.com> Reviewed-by: Pavel Snajdr <snajpa@snajpa.net> Reviewed-by: Alexander Motin <mav@FreeBSD.org> Reviewed-by: Kyle Evans <kevans@FreeBSD.org> Reviewed-by: Tony Hutter <hutter2@llnl.gov>
65 lines
2.3 KiB
C
65 lines
2.3 KiB
C
// SPDX-License-Identifier: CDDL-1.0
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/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or https://opensource.org/licenses/CDDL-1.0.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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/*
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* Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
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* Copyright 2015, Joyent, Inc. All rights reserved.
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* Copyright (c) 2016, Lawrence Livermore National Security, LLC.
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*/
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#ifndef _SYS_POLICY_H
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#define _SYS_POLICY_H
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#ifdef _KERNEL
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#include <sys/cred.h>
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#include <sys/types.h>
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#include <sys/xvattr.h>
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#include <sys/zpl.h>
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struct znode;
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int secpolicy_nfs(const cred_t *);
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int secpolicy_sys_config(const cred_t *, boolean_t);
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int secpolicy_vnode_access2(const cred_t *, struct inode *,
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uid_t, mode_t, mode_t);
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int secpolicy_vnode_any_access(const cred_t *, struct inode *, uid_t);
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int secpolicy_vnode_chown(const cred_t *, uid_t);
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int secpolicy_vnode_create_gid(const cred_t *);
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int secpolicy_vnode_remove(const cred_t *);
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int secpolicy_vnode_setdac(const cred_t *, uid_t);
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int secpolicy_vnode_setid_retain(struct znode *, const cred_t *, boolean_t);
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int secpolicy_vnode_setids_setgids(const cred_t *, gid_t, zidmap_t *,
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struct user_namespace *);
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int secpolicy_zinject(const cred_t *);
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int secpolicy_zfs(const cred_t *);
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void secpolicy_setid_clear(vattr_t *, cred_t *);
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int secpolicy_setid_setsticky_clear(struct inode *, vattr_t *,
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const vattr_t *, cred_t *, zidmap_t *, struct user_namespace *);
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int secpolicy_xvattr(xvattr_t *, uid_t, cred_t *, mode_t);
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int secpolicy_vnode_setattr(cred_t *, struct inode *, struct vattr *,
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const struct vattr *, int, int (void *, int, cred_t *), void *);
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int secpolicy_basic_link(const cred_t *);
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#endif /* _KERNEL */
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#endif /* _SYS_POLICY_H */
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