Date: Thu, 10 Sep 2009 00:58:34 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Chuck Ebbert <cebbert@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, torvalds@linux-foundation.org,
       dhowells@redhat.com, roland@redhat.com, jmorris@namei.org,
       tom.horsley@att.net, linux-kernel@vger.kernel.org, stable@kernel.org
Subject: Re: [PATCH v3] exec: do not sleep in TASK_TRACED under
	->cred_guard_mutex
Message-ID: <20090909225834.GA14785@redhat.com>
References: <20090904133956.GA9232@redhat.com> <20090903160514.GA23646@redhat.com> <20090903200924.E46DF47C94@magilla.sf.frob.com> <32710.1252075656@redhat.com> <20090904154947.GA17048@redhat.com> <20090904172648.GA25841@redhat.com> <20090904124230.5b7258c9.akpm@linux-foundation.org> <20090904213337.GA5021@redhat.com> <20090909175749.541b6aa9@dhcp-100-2-144.bos.redhat.com>
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On 09/09, Chuck Ebbert wrote:
>
> On Fri, 4 Sep 2009 23:33:37 +0200
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > On 09/04, Andrew Morton wrote:
> > >
> > > On Fri, 4 Sep 2009 19:26:48 +0200
> > > Oleg Nesterov <oleg@redhat.com> wrote:
> > >
> > > > Tom Horsley reports that his debugger hangs when it tries to read
> > > > /proc/pid_of_tracee/maps, this happens since
> > > >
> > > > 	"mm_for_maps: take ->cred_guard_mutex to fix the race with exec"
> > > > 	04b836cbf19e885f8366bccb2e4b0474346c02d
> > > >
> > > > commit in 2.6.31.
>
> >
> > > I see a Cc:stable in the mail headers, but not in the changelog.  I
> > > don't think the patch is applicable to -stable unless we miss 2.6.31.
> >
> > -stable has the same problems but I agree, it can live without this fix.
> >
>
> That patch was backported in 2.6.30.5 -- are you sure -stable doesn't need
> this fix?

No, I am not sure, that is why I cc'ed -stable.

But otoh the problem is minor, both tracer and tracee can be killed.

I dunno. I don't know if gdb or any other "important" application
read /proc/pid/maps after PTRACE_EVENT_EXEC...

Oleg.

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