linux-kernel - Re: ptrace && cred_exec_mutex (Was: [PATCH] ptrace: tracehook_unsafe

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Message-Id: <20090424193835.A765BFC3C7@magilla.sf.frob.com>
Date:	Fri, 24 Apr 2009 12:38:35 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
	James Morris <jmorris@...ei.org>,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: ptrace && cred_exec_mutex (Was: [PATCH] ptrace:
	tracehook_unsafe_exec: remove the stale comment)

> (change subject, add more CCs)
> 
> On 04/23, Roland McGrath wrote:
> >
> > > tracehook_unsafe_exec() doesn't need task_lock(), remove the old comment.
> >
> > Please make it instead say that cred_exec_mutex is held by the caller
> > through the exec.
> 
> Yes. Except it looks like ->cred_exec_mutex is never used in fact.
> 
> ptrace_attach() takes current->cred_exec_mutex ? iow, ptrace and exec
> use different locks ?

Good point!  That sure looks broken to me.  David?

Either that should be task->cred_exec_mutex, or Oleg and I
are completely confused about what cred_exec_mutex is meant for.


Thanks,
Roland
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