linux-kernel - Re: [PATCH -mm] Don't truncate /proc/PID/environ at 4096 characters

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Message-ID: <Pine.LNX.4.64.0709192023580.13121@blonde.wat.veritas.com>
Date:	Wed, 19 Sep 2007 20:29:07 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Mikael Pettersson <mikpe@...uu.se>
cc:	"H. Peter Anvin" <hpa@...or.com>, james-p@...ing-picture.com,
	linux-kernel@...r.kernel.org, aarapov@...hat.com,
	akpm@...ux-foundation.org
Subject: Re: [PATCH -mm] Don't truncate /proc/PID/environ at 4096 characters

On Wed, 19 Sep 2007, Mikael Pettersson wrote:
> H. Peter Anvin writes:
>  > Mikael Pettersson wrote:
>  > > Does /proc/PID/mem even work? If I do `strace cat /proc/PID/mem > /dev/null'
>  > > for a known good PID, the first read() from /proc/PID/mem fails with ESRCH,
>  > 
>  > Of course it does.  Address zero isn't typically mapped.
> 
> Indeed. My bad :-(

No, not quite.  Peter explains why "cat /proc/self/mem" gets EIO,
but you were seeing "cat /proc/other/mem" get ESRCH: that's from
the stringent !MAY_PTRACE || !ptrace_may_attach checks.

Hugh
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