[CRIU] [PATCH] restore: block SIGCHILD for sub-processes

[Andrew Vagin]

On Mon, Oct 05, 2015 at 07:03:45AM -0600, Tycho Andersen wrote:
> On Mon, Oct 05, 2015 at 02:56:06PM +0300, Andrey Vagin wrote:
> > From: Andrew Vagin <avagin at openvz.org>
> > 
> > Otherwise sigchld_handler() will call waitpid()
> > and worries about unknown process.
> > 
> > (00.333012)      1: kernel/hostname nr 15
> > (00.333120)      1: kernel/domainname nr 6
> > (00.335243)      1: Error (cr-restore.c:1225): BUG at cr-restore.c:1225
> > 
> > Cc: Tycho Andersen <tycho.andersen at canonical.com>
> 
> Whoops, somehow I didn't hit this when I ran the tests, thanks:
> 
> Acked-by: Tycho Andersen <tycho.andersen at canonical.com>

I found a small bug in this path, could you ack a second version of this
patch.

Thanks!

> 
> > Reported-by: Mr Jenkins
> > Signed-off-by: Andrew Vagin <avagin at openvz.org>
> > ---
> >  sysctl.c | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/sysctl.c b/sysctl.c
> > index e9fdf40..9a4bd1a 100644
> > --- a/sysctl.c
> > +++ b/sysctl.c
> > @@ -196,6 +196,7 @@ static int __userns_sysctl_op(void *arg, int unused, pid_t pid)
> >  	struct sysctl_userns_req *userns_req = arg;
> >  	int op = userns_req->op;
> >  	struct sysctl_req *req, **reqs = NULL;
> > +	sigset_t blockmask, oldmask;
> >  	pid_t worker;
> >  
> >  	// fix up the pointer
> > @@ -266,6 +267,16 @@ static int __userns_sysctl_op(void *arg, int unused, pid_t pid)
> >  		req = (struct sysctl_req *) (((char *) req) + total_len);
> >  	}
> >  
> > +	/*
> > +	 * Don't let the sigchld_handler() mess with us
> > +	 * calling waitpid() on the exited worker. The
> > +	 * same is done in cr_system().
> > +	 */
> > +
> > +	sigemptyset(&blockmask);
> > +	sigaddset(&blockmask, SIGCHLD);
> > +	sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
> > +
> >  	worker = fork();
> >  	if (worker < 0)
> >  		goto out;
> > @@ -310,6 +321,8 @@ static int __userns_sysctl_op(void *arg, int unused, pid_t pid)
> >  	ret = 0;
> >  
> >  out:
> > +	sigprocmask(SIG_BLOCK, &oldmask, NULL);
> > +
> >  	if (fds) {
> >  		for (i = 0; i < userns_req->nr_req; i++) {
> >  			if (fds[i] < 0)
> > -- 
> > 2.4.3
> >