[lxc-devel] [PATCH v2] fix console stdin,stdout,stderr fds
Dwight Engen
dwight.engen at oracle.com
Fri Mar 7 23:39:07 UTC 2014
On Fri, 7 Mar 2014 17:01:17 -0600
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.
> >
> > Signed-off-by: Dwight Engen <dwight.engen at oracle.com>
> > ---
> > src/lxc/console.c | 18 +++++++++++++++++-
> > src/lxc/console.h | 1 +
> > src/lxc/execute.c | 2 +-
> > src/lxc/lxc_console.c | 1 -
> > src/lxc/lxc_start.c | 1 -
> > src/lxc/start.c | 20 ++++++++++++++------
> > src/lxc/start.h | 2 +-
> > 7 files changed, 34 insertions(+), 11 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/execute.c b/src/lxc/execute.c
> > index b4f3ed9..e1b9ac7 100644
> > --- a/src/lxc/execute.c
> > +++ b/src/lxc/execute.c
> > @@ -162,7 +162,7 @@ int lxc_execute(const char *name, char *const
> > argv[], int quiet, .quiet = quiet
> > };
> >
> > - if (lxc_check_inherited(conf, -1))
> > + if (lxc_check_inherited(conf))
> > return -1;
> >
> > conf->is_execute = 1;
> > 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 eb1c659..8049870 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>
> > @@ -170,7 +169,7 @@ static int match_fd(int fd)
> > return (fd == 0 || fd == 1 || fd == 2);
> > }
> >
> > -int lxc_check_inherited(struct lxc_conf *conf, int fd_to_ignore)
> > +int lxc_check_inherited(struct lxc_conf *conf)
> > {
> > struct dirent dirent, *direntp;
> > int fd, fddir;
> > @@ -197,7 +196,7 @@ restart:
> >
> > fd = atoi(direntp->d_name);
> >
> > - if (fd == fddir || fd == lxc_log_fd || fd ==
> > fd_to_ignore)
> > + if (fd == fddir || fd == lxc_log_fd)
> > continue;
> >
> > if (match_fd(fd))
> > @@ -697,9 +696,6 @@ static int do_start(void *data)
> > if (lsm_process_label_set(lsm_label, 1, 1) < 0)
> > goto out_warn_father;
> >
> > - if (lxc_check_inherited(handler->conf, handler->sigfd))
> > - return -1;
> > -
> > /* If we mounted a temporary proc, then unmount it now */
> > tmp_proc_unmount(handler->conf);
> >
> > @@ -726,8 +722,20 @@ static int do_start(void *data)
> > 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;
> > +
> > close(handler->sigfd);
> >
> > + if (lxc_check_inherited(handler->conf))
> > + return -1;
> > +
>
> Hi,
>
> so the reason why the lxc_check_inherited() was where it
> was, was because at this point we've called tmp_proc_umount().
> So in some cases /proc won't be mounted, and lxc_check_inherited()
> finds the fds to close under /proc
Ahh okay that makes sense, good catch. So it seems like I should leave
lxc_check_inherited() where it was and then just put the call to
lxc_console_set_stdfds() just before it since it looks like
check_inherited() will leave 0,1,2 alone and close the original fds.
Does that sound reasonable?
> > /* after this call, we are in error because this
> > * ops should not return as it execs */
> > handler->ops->start(handler, handler->data);
> > diff --git a/src/lxc/start.h b/src/lxc/start.h
> > index e2d6bc8..17791b5 100644
> > --- a/src/lxc/start.h
> > +++ b/src/lxc/start.h
> > @@ -76,7 +76,7 @@ struct lxc_handler {
> >
> > extern struct lxc_handler *lxc_init(const char *name, struct
> > lxc_conf *, const char *);
> > -extern int lxc_check_inherited(struct lxc_conf *conf, int
> > fd_to_ignore); +extern int lxc_check_inherited(struct lxc_conf
> > *conf); int __lxc_start(const char *, struct lxc_conf *, struct
> > lxc_operations *, void *, const char *);
> >
> > --
> > 1.8.5.3
> >
> > _______________________________________________
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> > lxc-devel at lists.linuxcontainers.org
> > http://lists.linuxcontainers.org/listinfo/lxc-devel
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