Austin Group issue #411 [1] proposes that posix_spawn file action
posix_spawn_file_actions_adddup2 resets the close-on-exec when
source and destination refer to same file descriptor.
It solves the issue on multi-thread applications which uses
close-on-exec as default, and want to hand-chose specifically
file descriptor to purposefully inherited into a child process.
Current approach to achieve this scenario is to use two adddup2 file
actions and a temporary file description which do not conflict with
any other, coupled with a close file action to avoid leaking the
temporary file descriptor. This approach, besides being complex,
may fail with EMFILE/ENFILE file descriptor exaustion.
This can be more easily accomplished with an in-place removal of
FD_CLOEXEC. Although the resulting adddup2 semantic is slight
different than dup2 (equal file descriptors should be handled as
no-op), the proposed possible solution are either more complex
(fcntl action which a limited set of operations) or results in
unrequired operations (dup3 which also returns EINVAL for same
file descriptor).
Checked on aarch64-linux-gnu.
[BZ #23640]
* posix/tst-spawn.c (do_prepare, handle_restart, do_test): Add
posix_spawn_file_actions_adddup2 test to check O_CLOCEXEC reset.
* sysdeps/unix/sysv/linux/spawni.c (__spawni_child): Add
close-on-exec reset for adddup2 file action.
* sysdeps/posix/spawni.c (__spawni_child): Likewise.
[1] http://austingroupbugs.net/view.php?id=411
Otherwise, another user might recreate these files after the first
deletion. Particularly with temporary directories, this could result
in the removal of unintended files through symbol link attacks.
Current Linux posix_spawn spawn do not test if the pid argument is
valid before trying to update it for success case. This patch fixes
it.
Tested on x86_64 and i686.
* sysdeps/unix/sysv/linux/spawni.c (__spawnix): Fix invalid memory
access where posix_spawn success and pid argument is null.
* posix/tst-spawn.c (do_test): Add posix_spawn null pid argument for
success case.
POSIX requires that we make a copy, so we allocate a new string
and free it in posix_spawn_file_actions_destroy.
Reported by David Reid, Alex Gaynor, and Glyph Lefkowitz. This bug
may have security implications.
2001-07-06 Paul Eggert <eggert@twinsun.com>
* manual/argp.texi: Remove ignored LGPL copyright notice; it's
not appropriate for documentation anyway.
* manual/libc-texinfo.sh: "Library General Public License" ->
"Lesser General Public License".
2001-07-06 Andreas Jaeger <aj@suse.de>
* All files under GPL/LGPL version 2: Place under LGPL version
2.1.
Adhemerval Zanella
Joseph Myers
Szabolcs Nagy
Florian Weimer
Paul Pluzhnikov
Adhemerval Zanella
Allan McRae
H.J. Lu
Paul Eggert
Ulrich Drepper
Jakub Jelinek
Andreas Jaeger