[lxc-devel] [PATCH v3] fix console stdin,stdout,stderr fds
Stéphane Graber
stgraber at ubuntu.com
Fri Mar 21 19:00:11 UTC 2014
On Fri, Mar 21, 2014 at 11:19:21AM -0400, Dwight Engen wrote:
> 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.
Ah, I assumed Serge pushed it already, let me grab it from the archive
and send it then.
>
> > > ---
> > > 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
> > >
>
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--
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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