From: Dwight Engen <dwight.engen@oracle.com>
Date: Tue, 11 Mar 2014 19:44:54 +0000 (-0400)
Subject: fix console stdin,stdout,stderr fds
X-Git-Tag: lxc-1.1.0.alpha1~198
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0d9acb997fcb22ca6493535fd53ef0c4ee5bd156;p=thirdparty%2Flxc.git

fix console stdin,stdout,stderr fds

The fds for stdin,stdout,stderr that we were leaving open for /sbin/init
in the container were those from /dev/tty or lxc.console (if given), which
wasn't right. Inside the container it should only have access to the pty
that lxc creates representing the console.

This was noticed because busybox's init was resetting the termio on its
stdin which was effecting the actual users terminal instead of the pty.
This meant it was setting icanon so were were not passing keystrokes
immediately to the pty, and hence command line history/editing wasn't
working.

Fix by dup'ing the console pty to stdin,stdout,stderr just before
exec()ing /sbin/init. Fix fd leak in error handling that I noticed while
going through this code.

Also tested with lxc.console = none, lxc.console = /dev/tty7 and no
lxc.console specified.

V2: The first version was getting EBADF sometimes on dup2() because
lxc_console_set_stdfds() was being called after lxc_check_inherited()
had already closed the fds for the pty. Fix by calling
lxc_check_inherited() as late as possible which also extends coverage
of open fd checked code.

V3: Don't move lxc_check_inherited() since it needs to be called while
the tmp proc mount is still mounted. Move call to lxc_console_set_stdfds()
just before it.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
---

diff --git a/src/lxc/console.c b/src/lxc/console.c
index 6bfc8a34c..67e5d0f17 100644
--- a/src/lxc/console.c
+++ b/src/lxc/console.c
@@ -506,7 +506,7 @@ static void lxc_console_peer_default(struct lxc_console *console)
 	DEBUG("using '%s' as console", path);
 
 	if (!isatty(console->peer))
-		return;
+		goto err1;
 
 	ts = lxc_console_sigwinch_init(console->peer, console->master);
 	if (!ts)
@@ -611,7 +611,23 @@ err:
 	return -1;
 }
 
+int lxc_console_set_stdfds(struct lxc_handler *handler)
+{
+	struct lxc_conf *conf = handler->conf;
+	struct lxc_console *console = &conf->console;
+
+	if (console->slave < 0)
+		return 0;
 
+	if (dup2(console->slave, 0) < 0 ||
+	    dup2(console->slave, 1) < 0 ||
+	    dup2(console->slave, 2) < 0)
+	{
+		SYSERROR("failed to dup console");
+		return -1;
+	}
+	return 0;
+}
 
 static int lxc_console_cb_tty_stdin(int fd, uint32_t events, void *cbdata,
 				    struct lxc_epoll_descr *descr)
diff --git a/src/lxc/console.h b/src/lxc/console.h
index d45260cbe..eb3894b34 100644
--- a/src/lxc/console.h
+++ b/src/lxc/console.h
@@ -36,3 +36,4 @@ extern int  lxc_console(struct lxc_container *c, int ttynum,
 		        int escape);
 extern int  lxc_console_getfd(struct lxc_container *c, int *ttynum,
 			      int *masterfd);
+extern int  lxc_console_set_stdfds(struct lxc_handler *);
diff --git a/src/lxc/lxc_console.c b/src/lxc/lxc_console.c
index bfee6fb57..0fd08e879 100644
--- a/src/lxc/lxc_console.c
+++ b/src/lxc/lxc_console.c
@@ -28,7 +28,6 @@
 #include <errno.h>
 #include <string.h>
 #include <fcntl.h>
-#include <termios.h>
 #include <unistd.h>
 #include <signal.h>
 #include <libgen.h>
diff --git a/src/lxc/lxc_start.c b/src/lxc/lxc_start.c
index 05fb16113..d9a5694e7 100644
--- a/src/lxc/lxc_start.c
+++ b/src/lxc/lxc_start.c
@@ -27,7 +27,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
-#include <termios.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
diff --git a/src/lxc/start.c b/src/lxc/start.c
index 6b57ee119..ec1049640 100644
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -31,7 +31,6 @@
 #include <unistd.h>
 #include <signal.h>
 #include <fcntl.h>
-#include <termios.h>
 #include <grp.h>
 #include <poll.h>
 #include <sys/param.h>
@@ -697,6 +696,15 @@ static int do_start(void *data)
 	if (lsm_process_label_set(lsm_label, 1, 1) < 0)
 		goto out_warn_father;
 
+	/* Some init's such as busybox will set sane tty settings on stdin,
+	 * stdout, stderr which it thinks is the console. We already set them
+	 * the way we wanted on the real terminal, and we want init to do its
+	 * setup on its console ie. the pty allocated in lxc_console_create()
+	 * so make sure that that pty is stdin,stdout,stderr.
+	 */
+	if (lxc_console_set_stdfds(handler) < 0)
+		goto out_warn_father;
+
 	if (lxc_check_inherited(handler->conf, handler->sigfd))
 		return -1;