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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2016-09-16 17:44:50 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.com>2016-09-28 14:07:35 -0700
commite83be730910c341f2f02ccc207b0586bb04fc21a (patch)
tree6f8ff0de28073a7706be43359fa45fa50ea1b3f3 /posix
parent4b4d4056bb154603f36c6f8845757c1012758158 (diff)
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posix: Fix open file action for posix_spawn on Linux
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
Diffstat (limited to 'posix')
-rw-r--r--posix/Makefile2
-rw-r--r--posix/tst-spawn3.c189
2 files changed, 190 insertions, 1 deletions
diff --git a/posix/Makefile b/posix/Makefile
index 3a7719e..586d45b 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -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)
diff --git a/posix/tst-spawn3.c b/posix/tst-spawn3.c
new file mode 100644
index 0000000..7d5ffc6
--- /dev/null
+++ b/posix/tst-spawn3.c
@@ -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;
+}