From 3c9e5f28fc8ba0f14dde2f4c0ddecff0555c8d05 Mon Sep 17 00:00:00 2001
From: "Todd C. Miller" <Todd.Miller@courtesan.com>
Date: Tue, 31 May 2011 12:49:22 -0400
Subject: [PATCH] Fix compressed io log corruption in background mode by using
 _exit() instead of exit() to avoid flushing buffers twice.

Improved background mode support.  When not allocating a pty, the
command is run in its own process group.  This prevents write access
to the tty.  When running in a pty, stdin is not hooked up and we
never read from /dev/tty, which results in similar behavior.
---
 src/exec.c     | 11 +++++------
 src/exec_pty.c | 14 +++++++++-----
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/src/exec.c b/src/exec.c
index 3551ba531..52dbdbb1d 100644
--- a/src/exec.c
+++ b/src/exec.c
@@ -216,20 +216,19 @@ sudo_execve(struct command_details *details, struct command_status *cstat)
 		cstat->val = errno;
 		return -1;
 	    case 0:
-		/* child continues in a new session in a different pty */
-		SET(details->flags, CD_USE_PTY);
-		(void)setsid();
+		/* child continues without controlling terminal */
+		(void)setpgid(0, 0);
 		break;
 	    default:
-		/* parent exits */
-		exit(0);
+		/* parent exits (but does not flush buffers) */
+		_exit(0);
 	}
     }
 
     /*
      * If we have an I/O plugin or the policy plugin has requested one, we
      * need to allocate a pty.  It is OK to set log_io in the pty-only case
-     * as the tailqueue plugin will be empty and no I/O logging will occur.
+     * as the io plugin tailqueue will be empty and no I/O logging will occur.
      */
     if (!tq_empty(&io_plugins) || ISSET(details->flags, CD_USE_PTY)) {
 	log_io = TRUE;
diff --git a/src/exec_pty.c b/src/exec_pty.c
index 44d251f4c..b24d691b6 100644
--- a/src/exec_pty.c
+++ b/src/exec_pty.c
@@ -493,17 +493,21 @@ fork_pty(struct command_details *details, int sv[], int *maxfd)
 
     /*
      * Setup stdin/stdout/stderr for child, to be duped after forking.
+     * In background mode there is no stdin.
      */
-    io_fds[SFD_STDIN] = io_fds[SFD_SLAVE];
+    if (!ISSET(details->flags, CD_BACKGROUND))
+	io_fds[SFD_STDIN] = io_fds[SFD_SLAVE];
     io_fds[SFD_STDOUT] = io_fds[SFD_SLAVE];
     io_fds[SFD_STDERR] = io_fds[SFD_SLAVE];
 
-    /* Copy /dev/tty -> pty master */
     if (io_fds[SFD_USERTTY] != -1) {
-	iobufs = io_buf_new(io_fds[SFD_USERTTY], io_fds[SFD_MASTER],
-	    log_ttyin, iobufs);
+	/* Read from /dev/tty, write to pty master */
+	if (!ISSET(details->flags, CD_BACKGROUND)) {
+	    iobufs = io_buf_new(io_fds[SFD_USERTTY], io_fds[SFD_MASTER],
+		log_ttyin, iobufs);
+	}
 
-	/* Copy pty master -> /dev/tty */
+	/* Read from pty master, write to /dev/tty */
 	iobufs = io_buf_new(io_fds[SFD_MASTER], io_fds[SFD_USERTTY],
 	    log_ttyout, iobufs);