Date: Mon, 10 Nov 2008 15:54:10 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: adobriyan@gmail.com, kenchen@google.com, linux-kernel@vger.kernel.org,
       a.p.zijlstra@chello.nl
Subject: Re: [patch] add /proc/pid/stack to dump task's stack trace
Message-Id: <20081110155410.be7552e3.akpm@linux-foundation.org>
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On Fri, 7 Nov 2008 10:29:02 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> > I guess the 0400 mode on that file will suffice...
> 
> correct, 0400 is used already in the present patch:
> 
>  phoenix:~> cat /proc/1/stack
>  cat: /proc/1/stack: Permission denied
> 
> but that is _not_ enough, it should be narrowed even more, to the 
> boundaries that i pointed out in my first review feedback mail, and 
> which is not implemented yet:
> 
>  1) only root should be allowed to do this - i.e. file needs to be 
>     root-owned.
> 
>  2) there also needs to be a .config entry for folks to be able to
>     turn it off altogether - just like folks can turn off sysrq-t 
>     dumping via the .config.

Doing the above is desirable for another reason: given our rather
erratic history with the stack backtracer, this /proc file is possibly
a convenient way of oopsing the kernel, sending of off into la-la-land, etc.

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