[CRIU] [PATCH] fix segmentation fault caused by uninitialized mutex

[Cyrill Gorcunov]

On Fri, Jun 21, 2019 at 08:27:12PM -0700, Andrei Vagin wrote:
> Cyrill, could you review this patch?
> 
> On Wed, Jun 19, 2019 at 09:13:39AM +0000, Dengguangxing wrote:
> > 
> > Segmentation fault was raised while trying to restore a process with
> > tty. Coredump file says this is caused by uninitialized tty_mutex:
> >         (gdb) where
> >         #0  0x00000000004d7270 in atomic_add_return (i=1, v=0x0) at
> >         include/common/asm/atomic.h:34
> >         #1  0x00000000004d7398 in mutex_lock (m=0x0) at
> >         include/common/lock.h:151
> >         #2  0x00000000004d840c in __pty_open_ptmx_index (index=3, flags=2,
> >         cb=0x4dce50 <open_pty>, arg=0x11, path=0x5562e0 "ptmx") at
> >         criu/tty.c:603
> >         #3  0x00000000004dced8 in pty_create_ptmx_index (dfd=17, index=3,
> >         flags=2) at criu/tty.c:2384
> > 
> > since init_tty_mutex() is reentrantable, just calling it before
> > mutex_lock()
> > 
> > Signed-off-by: Deng Guangxing <dengguangxing at huawei.com>
> > ---
> >  criu/tty.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/criu/tty.c b/criu/tty.c
> > index 6fe11530..e9a28897 100644
> > --- a/criu/tty.c
> > +++ b/criu/tty.c
> > @@ -600,6 +600,9 @@ static int __pty_open_ptmx_index(int index, int flags,
> > 
> >         memset(fds, 0xff, sizeof(fds));
> > 
> > +       if (init_tty_mutex())
> > +               return -1;
> > +
> >         mutex_lock(tty_mutex);
> > 
> >         for (i = 0; i < ARRAY_SIZE(fds); i++) {

This should work but I don't like the whole design,
which is my fault. I'll rework it.

If we need a fast fix then

Reviewed-by: Cyrill Gorcunov <gorcunov at gmail.com>