Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec

[James Morris]

On Tue, 8 Feb 2011, Eric W. Biederman wrote:

> Kees Cook <kees.cook@xxxxxxxxxxxxx> writes:
> 
> > On Tue, Feb 08, 2011 at 02:43:15PM +1100, James Morris wrote:

> >> > I don't think /proc/$pid/* needs to stay open across execs, does it? Or at
> >> > least the non-0444 files should be handled separately.
> >> 
> >> Actually, this seems like a more general kind of bug in proc rather than a 
> >> leaked fd.  Each child task should only see its own /proc/[pid] data.
> >
> > Right, that's precisely the problem. The unprivileged process can read
> > the setuid process's /proc files.
> 
> If these are things that we actually care about we should sprinkle in a
> few more ptrace_may_access calls into implementations of the relevant
> proc files.

This seems to be papering over a bug.

It is plainly broken to return an access error to a task which is 
legitimately accessing a file.  The task should not receive the wrong 
information from /proc/[pid]/* .


- James
-- 
James Morris
<jmorris@xxxxxxxxx>
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