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GNU C Library master sources branch master updated. glibc-2.24-195-ge83be73
- From: azanella at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 28 Sep 2016 21:07:47 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.24-195-ge83be73
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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=e83be730910c341f2f02ccc207b0586bb04fc21a
commit e83be730910c341f2f02ccc207b0586bb04fc21a
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri Sep 16 17:44:50 2016 -0300
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
diff --git a/ChangeLog b/ChangeLog
index e05b877..6d6e668 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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.
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;
+}
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index 679534b..fda8593 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -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,
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=4b4d4056bb154603f36c6f8845757c1012758158
commit 4b4d4056bb154603f36c6f8845757c1012758158
Author: Rasmus Villemoes <rv@rasmusvillemoes.dk>
Date: Tue Sep 27 17:52:17 2016 -0700
linux: spawni.c: simplify error reporting to parent
Using CLONE_VFORK already ensures that the parent does not run until the
child has either exec'ed succesfully or called _exit. Hence we don't
need to read from a CLOEXEC pipe to ensure proper synchronization - we
just make explicit use of the fact the the child and parent run in the
same VM, so the child can write an error code to a field of the
posix_spawn_args struct instead of sending it through a pipe.
To ensure that this mechanism really works, the parent initializes the
field to -1 and the child writes 0 before execing.
This eliminates some annoying bookkeeping that is necessary to avoid
the file actions from clobbering the write end of the pipe, and
getting rid of the pipe creation in the first place means fewer system
calls (four in the parent, usually one in the child) and fewer
chanches for the spawn to fail (e.g. if we're close to EMFILE).
Checked on x86_64 and i686.
* sysdeps/unix/sysv/linux/spawni.c (posix_spawn_args): Remove pipe
field, add err field.
(__spawni_child): Report error through err member instead of pipe.
(__spawnix): Likewise.
diff --git a/ChangeLog b/ChangeLog
index 88ea4b1..e05b877 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2016-09-28 Rasmus Villemoes <rv@rasmusvillemoes.dk>
+
+ * sysdeps/unix/sysv/linux/spawni.c (posix_spawn_args): Remove pipe
+ field, add err field.
+ (__spawni_child): Report error through err member instead of pipe.
+ (__spawnix): Likewise.
+
2016-09-28 Zack Weinberg <zackw@panix.com>
* scripts/check-installed-headers.sh: Generalize treatment of
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index 67e1c42..679534b 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -17,6 +17,7 @@
<http://www.gnu.org/licenses/>. */
#include <spawn.h>
+#include <assert.h>
#include <fcntl.h>
#include <paths.h>
#include <string.h>
@@ -44,11 +45,12 @@
3. Child must synchronize with parent to enforce 2. and to possible
return execv issues.
- The first issue is solved by blocking all signals in child, even the
- NPTL-internal ones (SIGCANCEL and SIGSETXID). The second and third issue
- is done by a stack allocation in parent and a synchronization with using
- a pipe or waitpid (in case or error). The pipe has the advantage of
- allowing the child the communicate an exec error. */
+ The first issue is solved by blocking all signals in child, even
+ the NPTL-internal ones (SIGCANCEL and SIGSETXID). The second and
+ third issue is done by a stack allocation in parent, and by using a
+ field in struct spawn_args where the child can write an error
+ code. CLONE_VFORK ensures that the parent does not run until the
+ child has either exec'ed successfully or exited. */
/* The Unix standard contains a long explanation of the way to signal
@@ -75,7 +77,6 @@
struct posix_spawn_args
{
- int pipe[2];
sigset_t oldmask;
const char *file;
int (*exec) (const char *, char *const *, char *const *);
@@ -85,6 +86,7 @@ struct posix_spawn_args
ptrdiff_t argc;
char *const *envp;
int xflags;
+ int err;
};
/* Older version requires that shell script without shebang definition
@@ -121,11 +123,8 @@ __spawni_child (void *arguments)
struct posix_spawn_args *args = arguments;
const posix_spawnattr_t *restrict attr = args->attr;
const posix_spawn_file_actions_t *file_actions = args->fa;
- int p = args->pipe[1];
int ret;
- close_not_cancel (args->pipe[0]);
-
/* The child must ensure that no signal handler are enabled because it shared
memory with parent, so the signal disposition must be either SIG_DFL or
SIG_IGN. It does by iterating over all signals and although it could
@@ -199,17 +198,6 @@ __spawni_child (void *arguments)
{
struct __spawn_action *action = &file_actions->__actions[cnt];
- /* Dup the pipe fd onto an unoccupied one to avoid any file
- operation to clobber it. */
- if ((action->action.close_action.fd == p)
- || (action->action.open_action.fd == p)
- || (action->action.dup2_action.fd == p))
- {
- if ((ret = __dup (p)) < 0)
- goto fail;
- p = ret;
- }
-
switch (action->tag)
{
case spawn_do_close:
@@ -269,6 +257,7 @@ __spawni_child (void *arguments)
__sigprocmask (SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
? &attr->__ss : &args->oldmask, 0);
+ args->err = 0;
args->exec (args->file, args->argv, args->envp);
/* This is compatibility function required to enable posix_spawn run
@@ -276,14 +265,13 @@ __spawni_child (void *arguments)
(2.15). */
maybe_script_execute (args);
- ret = -errno;
-
fail:
- /* Since sizeof errno < PIPE_BUF, the write is atomic. */
- ret = -ret;
- if (ret)
- while (write_not_cancel (p, &ret, sizeof ret) < 0)
- continue;
+ /* errno should have an appropriate non-zero value; otherwise,
+ there's a bug in glibc or the kernel. For lack of an error code
+ (EINTERNALBUG) describing that, use ECHILD. Another option would
+ be to set args->err to some negative sentinel and have the parent
+ abort(), but that seems needlessly harsh. */
+ args->err = errno ? : ECHILD;
_exit (SPAWN_ERROR);
}
@@ -300,9 +288,6 @@ __spawnix (pid_t * pid, const char *file,
struct posix_spawn_args args;
int ec;
- if (__pipe2 (args.pipe, O_CLOEXEC))
- return errno;
-
/* To avoid imposing hard limits on posix_spawn{p} the total number of
arguments is first calculated to allocate a mmap to hold all possible
values. */
@@ -329,17 +314,16 @@ __spawnix (pid_t * pid, const char *file,
void *stack = __mmap (NULL, stack_size, prot,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (__glibc_unlikely (stack == MAP_FAILED))
- {
- close_not_cancel (args.pipe[0]);
- close_not_cancel (args.pipe[1]);
- return errno;
- }
+ return errno;
/* Disable asynchronous cancellation. */
int state;
__libc_ptf_call (__pthread_setcancelstate,
(PTHREAD_CANCEL_DISABLE, &state), 0);
+ /* Child must set args.err to something non-negative - we rely on
+ the parent and child sharing VM. */
+ args.err = -1;
args.file = file;
args.exec = exec;
args.fa = file_actions;
@@ -353,9 +337,8 @@ __spawnix (pid_t * pid, const char *file,
/* The clone flags used will create a new child that will run in the same
memory space (CLONE_VM) and the execution of calling thread will be
- suspend until the child calls execve or _exit. These condition as
- signal below either by pipe write (_exit with SPAWN_ERROR) or
- a successful execve.
+ suspend until the child calls execve or _exit.
+
Also since the calling thread execution will be suspend, there is not
need for CLONE_SETTLS. Although parent and child share the same TLS
namespace, there will be no concurrent access for TLS variables (errno
@@ -363,22 +346,18 @@ __spawnix (pid_t * pid, const char *file,
new_pid = CLONE (__spawni_child, STACK (stack, stack_size), stack_size,
CLONE_VM | CLONE_VFORK | SIGCHLD, &args);
- close_not_cancel (args.pipe[1]);
-
if (new_pid > 0)
{
- if (__read (args.pipe[0], &ec, sizeof ec) != sizeof ec)
- ec = 0;
- else
- __waitpid (new_pid, NULL, 0);
+ ec = args.err;
+ assert (ec >= 0);
+ if (ec != 0)
+ __waitpid (new_pid, NULL, 0);
}
else
ec = -new_pid;
__munmap (stack, stack_size);
- close_not_cancel (args.pipe[0]);
-
if ((ec == 0) && (pid != NULL))
*pid = new_pid;
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 12 +++
posix/Makefile | 2 +-
posix/tst-spawn3.c | 189 ++++++++++++++++++++++++++++++++++++++
sysdeps/unix/sysv/linux/spawni.c | 79 +++++++---------
4 files changed, 235 insertions(+), 47 deletions(-)
create mode 100644 posix/tst-spawn3.c
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