[lxc-devel] [PATCH v3] fix console stdin,stdout,stderr fds

[Dwight Engen]

On Tue, 11 Mar 2014 23:06:22 -0500
Serge Hallyn <serge.hallyn at ubuntu.com> wrote:

> Quoting Dwight Engen (dwight.engen at oracle.com):
> > 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 at oracle.com>
> 
> looks good, thanks!
> 
> Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

Hi, I think maybe this one missed being pushed, unless I missed
something else that needed to be fixed up with it.

> > ---
> >  src/lxc/console.c     | 18 +++++++++++++++++-
> >  src/lxc/console.h     |  1 +
> >  src/lxc/lxc_console.c |  1 -
> >  src/lxc/lxc_start.c   |  1 -
> >  src/lxc/start.c       | 10 +++++++++-
> >  5 files changed, 27 insertions(+), 4 deletions(-)
> > 
> > diff --git a/src/lxc/console.c b/src/lxc/console.c
> > index 6bfc8a3..67e5d0f 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 d45260c..eb3894b 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 bfee6fb..0fd08e8 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 05fb161..d9a5694 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 6b57ee1..ec10496 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;
> >  
> > -- 
> > 1.8.5.3
> >