Re: [RFC PATCH 1/5] lguest: mmap backing file

[Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>]

On Thursday 20 March 2008 19:16:00 Tim Post wrote:
> On Thu, 2008-03-20 at 17:05 +1100, Rusty Russell wrote:
> > +       snprintf(memfile_path, PATH_MAX, "%s/.lguest",
> > getenv("HOME") ?: "");
>
> Hi Rusty,
>
> Is that safe if being run via setuid/gid or shared root? It might be
> better to just look it up in /etc/passwd against the real UID,
> considering that anyone can change (or null) that env string.

Hi Tim,

    Fair point: it is bogus in this usage case.  Of course, setuid-ing lguest 
is dumb anyway, since you could use --block= to read and write any file in 
the filesystem.  The mid-term goal is to allow non-root to run lguest, which 
fixes this problem (we don't allow that at the moment, as the guest can pin 
memory).

Cheers,
Rusty.