From: Paolo Bonzini <bonzini@gnu.org>
Date: Wed, 27 Aug 2008 08:20:23 GMT
Subject: Re: [PATCH] be paranoid about closed stdin/stdout/stderr
Message-ID: <48B50E47.3010402@gnu.org>
In-Reply-To: <48B4F5C4.9020404@viscovery.net>


>> Busybox.  But it runs setuid, as Steven pointed out.
> 
> I straced tee (it was the only tool I found that opens files for writing
> without also opening some for reading). If one of 0,1,2 is closed, it
> *does* dup() the fd that it is going to write.

To be precise, it does a blind "dup2 (fd, 3)" and goes on with file
descriptor 3.

open("foo", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 0
fcntl64(0, F_DUPFD, 3)                  = 3
close(0)                                = 0

Paolo