Re: [Xen-devel] [PATCH v2] xl: close nullfd after dup2'ing it to stdin

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Feb 23, 2016 at 10:30:31AM +0000, Ian Campbell wrote:
> On Wed, 2016-02-17 at 10:39 +0000, Ian Campbell wrote:
> > We assert that nullfd if not std{in,out,err} since that would result
> > in closing one of the just dup2'd fds. For this to happen
> > std{in,out,err} would have needed to be closed, at which point all
> > sorts of other things could go wrong.
> > 
> > CID: 1130519
> > 
> > It was previously hypothesised[0] that fixing 1130516 would solve this
> > too, but that appears to not have been the case.
> > 
> > Compile tested only.
> > 
> > [0] http://lists.xenproject.org/archives/html/xen-devel/2013-11/msg02931.
> > html
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > Cc: andrew.cooper3@xxxxxxxxxx
> 
> ping?

Ian, you wouldn't have a git branch with all your outstanding
patches you had posted somewhere?

Just in case we don't get to them done by feature freeze window and
somebody starts replaying these patches..

> 
> > ---
> > v2: Assert logfile and nullfd are not stdio fds
> > ---
> >  tools/libxl/xl_cmdimpl.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> > index 9958d8a..a377de1 100644
> > --- a/tools/libxl/xl_cmdimpl.c
> > +++ b/tools/libxl/xl_cmdimpl.c
> > @@ -499,12 +499,17 @@ static int do_daemonize(char *name, const char
> > *pidfile)
> >  
> >      CHK_SYSCALL(logfile = open(fullname, O_WRONLY|O_CREAT|O_APPEND,
> > 0644));
> >      free(fullname);
> > +    assert(logfile >= 3);
> >  
> >      CHK_SYSCALL(nullfd = open("/dev/null", O_RDONLY));
> > +    assert(nullfd >= 3);
> > +
> >      dup2(nullfd, 0);
> >      dup2(logfile, 1);
> >      dup2(logfile, 2);
> >  
> > +    close(nullfd);
> > +
> >      CHK_SYSCALL(daemon(0, 1));
> >  
> >      if (pidfile) {
> 
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