Attachment 135468 Details for Bug 103601 – [08/13] Unix: Flush stdout and stderr streams before forking

[patch] [08/13] Unix: Flush stdout and stderr streams before forking

0008-Unix-Flush-stdout-and-stderr-streams-before-forking.patch (text/plain), 5.60 KB, created by Simon McVittie on 2017-11-14 19:10:48 UTC

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Creator: Simon McVittie

Created: 2017-11-14 19:10:48 UTC

Size: 5.60 KB

patch

obsolete

>From 2fb23fe9624c39d0e903b4df8cbffcd1090f6682 Mon Sep 17 00:00:00 2001
>From: Simon McVittie <smcv@collabora.com>
>Date: Tue, 14 Nov 2017 15:30:03 +0000
>Subject: [PATCH 08/13] Unix: Flush stdout and stderr streams before forking
>
>stdout and stderr are close-on-exec and buffered, so we can't rely on
>their buffers being empty. If we continue to execute application code
>after forking (as opposed to immediately exec()ing), then the child
>process might later flush the libc stdio buffers, resulting in
>output that is printed by the parent also being printed by the child.
>
>In particular, test-bus.log sometimes grows extremely large for
>this reason, because this test repeatedly attempts to carry out
>legacy activation.
>
>Signed-off-by: Simon McVittie <smcv@collabora.com>
>---
> dbus/dbus-spawn.c             | 11 ++++++++++-
> dbus/dbus-sysdeps-unix.c      | 10 ++++++++++
> dbus/dbus-sysdeps-util-unix.c |  7 +++++++
> test/test-service.c           | 10 +++++++++-
> tools/dbus-launch.c           | 14 +++++++++++++-
> tools/dbus-run-session.c      |  8 ++++++++
> 6 files changed, 57 insertions(+), 3 deletions(-)
>
>diff --git a/dbus/dbus-spawn.c b/dbus/dbus-spawn.c
>index 8ab529a4..b2bcc226 100644
>--- a/dbus/dbus-spawn.c
>+++ b/dbus/dbus-spawn.c
>@@ -34,6 +34,7 @@
> #include <fcntl.h>
> #include <signal.h>
> #include <sys/wait.h>
>+#include <stdio.h>
> #include <stdlib.h>
> #ifdef HAVE_ERRNO_H
> #include <errno.h>
>@@ -1362,6 +1363,11 @@ _dbus_spawn_async_with_babysitter (DBusBabysitter          **sitter_p,
>     }
> #endif
> 
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   pid = fork ();
>   
>   if (pid < 0)
>@@ -1385,7 +1391,10 @@ _dbus_spawn_async_with_babysitter (DBusBabysitter          **sitter_p,
>       /* Close the parent's end of the pipes. */
>       close_and_invalidate (&child_err_report_pipe[READ_END]);
>       close_and_invalidate (&babysitter_pipe[0].fd);
>-      
>+
>+      fflush (stdout);
>+      fflush (stderr);
>+
>       /* Create the child that will exec () */
>       grandchild_pid = fork ();
>       
>diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
>index bebf2073..f103323c 100644
>--- a/dbus/dbus-sysdeps-unix.c
>+++ b/dbus/dbus-sysdeps-unix.c
>@@ -1040,6 +1040,11 @@ _dbus_connect_exec (const char     *path,
>       _dbus_fd_set_close_on_exec (fds[1]);
>     }
> 
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   pid = fork ();
>   if (pid < 0)
>     {
>@@ -3623,6 +3628,11 @@ _read_subprocess_line_argv (const char *progpath,
>       goto out;
>     }
> 
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   pid = fork ();
>   if (pid < 0)
>     {
>diff --git a/dbus/dbus-sysdeps-util-unix.c b/dbus/dbus-sysdeps-util-unix.c
>index 2be5b779..b841bf63 100644
>--- a/dbus/dbus-sysdeps-util-unix.c
>+++ b/dbus/dbus-sysdeps-util-unix.c
>@@ -35,6 +35,7 @@
> #include "dbus-test.h"
> 
> #include <sys/types.h>
>+#include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <signal.h>
>@@ -99,6 +100,12 @@ _dbus_become_daemon (const DBusString *pidfile,
>     }
> 
>   _dbus_verbose ("forking...\n");
>+
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   switch ((child_pid = fork ()))
>     {
>     case -1:
>diff --git a/test/test-service.c b/test/test-service.c
>index b500af31..f71e3e03 100644
>--- a/test/test-service.c
>+++ b/test/test-service.c
>@@ -1,6 +1,7 @@
> #include <config.h>
> 
> #include "test-utils.h"
>+#include <stdio.h>
> #ifdef HAVE_UNISTD_H
> #include <unistd.h>
> #endif
>@@ -424,7 +425,14 @@ main (int    argc,
> #ifndef DBUS_WIN
>    if (do_fork)
>     {
>-      pid_t pid = fork ();
>+      pid_t pid;
>+
>+      /* Make sure our output buffers aren't redundantly printed by both the
>+       * parent and the child */
>+      fflush (stdout);
>+      fflush (stderr);
>+
>+      pid = fork ();
>       if (pid != 0)
>         exit (0);
>       sleep (1);
>diff --git a/tools/dbus-launch.c b/tools/dbus-launch.c
>index f5287548..425914a1 100644
>--- a/tools/dbus-launch.c
>+++ b/tools/dbus-launch.c
>@@ -656,6 +656,11 @@ babysit (int   exit_with_session,
>       exit (1);
>     }
> 
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   ret = fork ();
> 
>   if (ret < 0)
>@@ -1125,6 +1130,11 @@ main (int argc, char **argv)
>       exit (1);
>     }
> 
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   ret = fork ();
>   if (ret < 0)
>     {
>@@ -1150,7 +1160,9 @@ main (int argc, char **argv)
>       verbose ("=== Babysitter's intermediate parent created\n");
> 
>       /* Fork once more to create babysitter */
>-      
>+
>+      fflush (stdout);
>+      fflush (stderr);
>       ret = fork ();
>       if (ret < 0)
>         {
>diff --git a/tools/dbus-run-session.c b/tools/dbus-run-session.c
>index 0adb5ad1..6b93997e 100644
>--- a/tools/dbus-run-session.c
>+++ b/tools/dbus-run-session.c
>@@ -354,6 +354,11 @@ main (int argc, char **argv)
>       return 127;
>     }
> 
>+  /* Make sure our output buffers aren't redundantly printed by both the
>+   * parent and the child */
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   bus_pid = fork ();
> 
>   if (bus_pid < 0)
>@@ -401,6 +406,9 @@ main (int argc, char **argv)
>       !dbus_setenv ("DBUS_STARTER_BUS_TYPE", NULL))
>     oom ();
> 
>+  fflush (stdout);
>+  fflush (stderr);
>+
>   app_pid = fork ();
> 
>   if (app_pid < 0)
>-- 
>2.15.0
>

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Attachments on bug 103601: 135460 | 135462 | 135463 | 135464 | 135465 | 135466 | 135467 | 135468 | 135469 | 135470 | 135471 | 135472 | 135473 | 135485

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