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/*
Unix SMB/Netbios implementation.
Copyright (C) Ralph Boehme 2019
Copyright (C) Stefan Metzmacher 2019
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include "system/filesys.h"
#include "system/threads.h"
#ifdef HAVE_UNSHARE_CLONE_FS
#include <sched.h>
#endif /* HAVE_UNSHARE_CLONE_FS */
static bool _per_thread_cwd_checked;
static bool _per_thread_cwd_supported;
#ifdef HAVE_UNSHARE_CLONE_FS
static __thread bool _per_thread_cwd_disabled;
static __thread bool _per_thread_cwd_activated;
#endif /* HAVE_UNSHARE_CLONE_FS */
/*
* This is the first function to be called!
* Typically in the main() function before
* any threads are created.
*
* This can be called multiple times
* as the result is cached the first time.
*/
void per_thread_cwd_check(void)
{
if (_per_thread_cwd_checked) {
return;
}
#ifdef HAVE_UNSHARE_CLONE_FS
/*
* While unshare(CLONE_FS) is available on
* Linux for ages, unshare() is also
* used to implement containers with various
* per container namespaces.
*
* It's possible that the whole unshare()
* is blocked in order to disallow nested
* containers.
*
* That's why we sadly need a runtime check
* for this.
*/
{
int res;
res = unshare(CLONE_FS);
if (res == 0) {
_per_thread_cwd_supported = true;
}
}
/*
* We're in the main thread, so we should disallow
* per_thread_cwd_activate() here.
*/
_per_thread_cwd_disabled = true;
#endif /* HAVE_UNSHARE_CLONE_FS */
_per_thread_cwd_checked = true;
}
/*
* In order to use per_thread_cwd_supported()
* per_thread_cwd_check() needs to be called first!
* Otherwise an assert will be triggered!
*/
bool per_thread_cwd_supported(void)
{
SMB_ASSERT(_per_thread_cwd_checked);
return _per_thread_cwd_supported;
}
/*
* In order to use per_thread_cwd_disable()
* should be called after any fork() in order
* to mark the main thread of the process,
* which should disallow per_thread_cwd_activate().
*
* This can be called without calling
* per_thread_cwd_check() first.
*
* And it can't be called after calling
* per_thread_cwd_activate()!
* Otherwise an assert will be triggered!
*
* This can be called multiple times
* as the result is cached the first time.
*/
void per_thread_cwd_disable(void)
{
#ifdef HAVE_UNSHARE_CLONE_FS
SMB_ASSERT(!_per_thread_cwd_activated);
if (_per_thread_cwd_disabled) {
return;
}
_per_thread_cwd_disabled = true;
#endif /* HAVE_UNSHARE_CLONE_FS */
}
/*
* In order to use per_thread_cwd_activate()
* per_thread_cwd_supported() needs to be checked first!
* Otherwise an assert will be triggered!
*
* This MUST only be called within helper threads!
*
* That means it can't be called after calling
* per_thread_cwd_disable()!
* Otherwise an assert will be triggered!
*
* This can be called multiple times
* as the result is cached the first time.
*/
void per_thread_cwd_activate(void)
{
SMB_ASSERT(_per_thread_cwd_checked);
SMB_ASSERT(_per_thread_cwd_supported);
#ifdef HAVE_UNSHARE_CLONE_FS
if (_per_thread_cwd_activated) {
return;
}
SMB_ASSERT(!_per_thread_cwd_disabled);
{
int ret;
ret = unshare(CLONE_FS);
SMB_ASSERT(ret == 0);
}
_per_thread_cwd_activated = true;
#else /* not HAVE_UNSHARE_CLONE_FS */
smb_panic(__location__);
#endif /* not HAVE_UNSHARE_CLONE_FS */
}
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