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posix: Fix open file action for posix_spawn on Linux

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On posix_spawn open file action (issued by posix_spawn_file_actions_addopen)
POSIX states that if fildes was already an open file descriptor, it shall be
closed before the new file is openedi [1].  This avoid pontential issues when
posix_spawn plus addopen action is called with the process already at maximum
number of file descriptor opened and also for multiple actions on single-open
special paths (like /dev/watchdog).

This fixes its behavior on Linux posix_spawn implementation and also adds
a tests to check for its behavior.

Checked on x86_64.

	* posix/Makefile (tests): Add tst-spawn3.
	* posix/tst-spawn3.c: New file.
	* sysdeps/unix/sysv/linux/spawni.c (__spawni_child): Close file descriptor
	if it is already opened for open action.

[1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn_file_actions_addclose.html
This commit is contained in:
Adhemerval Zanella
2016-09-16 17:44:50 -03:00
committed by Adhemerval Zanella
parent 4b4d4056bb
commit e83be73091
4 changed files with 203 additions and 1 deletions
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8
sysdeps/unix/sysv/linux/spawni.c
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@ -219,6 +219,14 @@ __spawni_child (void *arguments)
case spawn_do_open:
{
/* POSIX states that if fildes was already an open file descriptor,
it shall be closed before the new file is opened. This avoid
pontential issues when posix_spawn plus addopen action is called
with the process already at maximum number of file descriptor
opened and also for multiple actions on single-open special
paths (like /dev/watchdog). */
close_not_cancel (action->action.open_action.fd);
ret = open_not_cancel (action->action.open_action.path,
action->action.
open_action.oflag | O_LARGEFILE,