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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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5
ChangeLog
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@ -497,6 +497,11 @@
2016-09-20 Adhemerval Zanella <adhemerval.zanella@linaro.org>
* 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.
* sysdeps/unix/sysv/linux/spawni.c (__spawnix): Correctly block and unblock
all signals when executing the clone vfork child.
(SIGALL_SET): Remove macro.

2
posix/Makefile
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@ -94,7 +94,7 @@ tests := tstgetopt testfnm runtests runptests \
xtests := bug-ga2
ifeq (yes,$(build-shared))
test-srcs := globtest
tests += wordexp-test tst-exec tst-spawn tst-spawn2
tests += wordexp-test tst-exec tst-spawn tst-spawn2 tst-spawn3
endif
tests-static = tst-exec-static tst-spawn-static
tests += $(tests-static)

189
posix/tst-spawn3.c Normal file
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@ -0,0 +1,189 @@
/* Check posix_spawn add file actions.
Copyright (C) 2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <spawn.h>
#include <error.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/resource.h>
static int do_test (void);
#define TEST_FUNCTION do_test ()
#include <test-skeleton.c>
static int
do_test (void)
{
/* The test checks if posix_spawn open file action close the file descriptor
before opening a new one in case the input file descriptor is already
opened. It does by exhausting all file descriptors on the process before
issue posix_spawn. It then issues a posix_spawn for '/bin/sh echo $$'
and add two rules:
1. Redirect stdout to a temporary filepath
2. Redirect stderr to stdout
If the implementation does not close the file 1. will fail with
EMFILE. */
struct rlimit rl;
int max_fd = 24;
/* Set maximum number of file descriptor to a low value to avoid open
too many files in environments where RLIMIT_NOFILE is large and to
limit the array size to track the opened file descriptors. */
if (getrlimit (RLIMIT_NOFILE, &rl) == -1)
{
printf ("error: getrlimit RLIMIT_NOFILE failed");
exit (EXIT_FAILURE);
}
max_fd = (rl.rlim_cur < max_fd ? rl.rlim_cur : max_fd);
rl.rlim_cur = max_fd;
if (setrlimit (RLIMIT_NOFILE, &rl) == 1)
{
printf ("error: setrlimit RLIMIT_NOFILE to %u failed", max_fd);
exit (EXIT_FAILURE);
}
/* Exhauste the file descriptor limit with temporary files. */
int files[max_fd];
int nfiles = 0;
for (;;)
{
int fd = create_temp_file ("tst-spawn3.", NULL);
if (fd == -1)
{
if (errno != EMFILE)
{
printf ("error: create_temp_file returned -1 with "
"errno != EMFILE\n");
exit (EXIT_FAILURE);
}
break;
}
files[nfiles++] = fd;
}
posix_spawn_file_actions_t a;
if (posix_spawn_file_actions_init (&a) != 0)
{
puts ("error: spawn_file_actions_init failed");
exit (EXIT_FAILURE);
}
/* Executes a /bin/sh echo $$ 2>&1 > /tmp/tst-spawn3.pid . */
const char pidfile[] = "/tmp/tst-spawn3.pid";
if (posix_spawn_file_actions_addopen (&a, STDOUT_FILENO, pidfile, O_WRONLY |
O_CREAT | O_TRUNC, 0644) != 0)
{
puts ("error: spawn_file_actions_addopen failed");
exit (EXIT_FAILURE);
}
if (posix_spawn_file_actions_adddup2 (&a, STDOUT_FILENO, STDERR_FILENO) != 0)
{
puts ("error: spawn_file_actions_addclose");
exit (EXIT_FAILURE);
}
/* Since execve (called by posix_spawn) might require to open files to
actually execute the shell script, setup to close the temporary file
descriptors. */
for (int i=0; i<nfiles; i++)
{
if (posix_spawn_file_actions_addclose (&a, files[i]))
{
printf ("error: posix_spawn_file_actions_addclose failed");
exit (EXIT_FAILURE);
}
}
char *spawn_argv[] = { (char *) _PATH_BSHELL, (char *) "-c",
(char *) "echo $$", NULL };
pid_t pid;
if (posix_spawn (&pid, _PATH_BSHELL, &a, NULL, spawn_argv, NULL) != 0)
{
puts ("error: posix_spawn failed");
exit (EXIT_FAILURE);
}
int status;
int err = waitpid (pid, &status, 0);
if (err != pid)
{
puts ("error: waitpid failed");
exit (EXIT_FAILURE);
}
/* Close the temporary files descriptor so it can check posix_spawn
output. */
for (int i=0; i<nfiles; i++)
{
if (close (files[i]))
{
printf ("error: close failed\n");
exit (EXIT_FAILURE);
}
}
int pidfd = open (pidfile, O_RDONLY);
if (pidfd == -1)
{
printf ("error: open pidfile failed\n");
exit (EXIT_FAILURE);
}
char buf[64];
ssize_t n;
if ((n = read (pidfd, buf, sizeof (buf))) < 0)
{
printf ("error: read pidfile failed\n");
exit (EXIT_FAILURE);
}
unlink (pidfile);
/* We only expect to read the PID. */
char *endp;
long int rpid = strtol (buf, &endp, 10);
if (*endp != '\n')
{
printf ("error: didn't parse whole line: \"%s\"\n", buf);
exit (EXIT_FAILURE);
}
if (endp == buf)
{
puts ("error: read empty line");
exit (EXIT_FAILURE);
}
if (rpid != pid)
{
printf ("error: found \"%s\", expected PID %ld\n", buf, (long int) pid);
exit (EXIT_FAILURE);
}
return 0;
}

8
sysdeps/unix/sysv/linux/spawni.c
View File

@ -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,