From 8daa83a594a2e98f39d764422bfbdbc62c9efd44 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Fri, 19 Apr 2024 19:20:00 +0200 Subject: Adding upstream version 2:4.20.0+dfsg. Signed-off-by: Daniel Baumann --- source3/lib/per_thread_cwd.c | 156 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 156 insertions(+) create mode 100644 source3/lib/per_thread_cwd.c (limited to 'source3/lib/per_thread_cwd.c') diff --git a/source3/lib/per_thread_cwd.c b/source3/lib/per_thread_cwd.c new file mode 100644 index 0000000..b71d4c6 --- /dev/null +++ b/source3/lib/per_thread_cwd.c @@ -0,0 +1,156 @@ +/* + 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 . +*/ + +#include "includes.h" +#include "system/filesys.h" +#include "system/threads.h" +#ifdef HAVE_UNSHARE_CLONE_FS +#include +#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 */ +} -- cgit v1.2.3