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Subject: Re: [PATCH v3] sysctl: control functionality of /proc/pid/mem
From: Colin Walters <walters@verbum.org>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Randy Dunlap <rdunlap@xenotime.net>, Borislav Petkov <bp@alien8.de>,
        Vasiliy Kulikov <segoon@openwall.com>, Dan Ballard <dan@mindstab.net>,
        Jiri Kosina <jkosina@suse.cz>, Al Viro <viro@zeniv.linux.org.uk>,
        Stephen Wilson <wilsons@start.ca>,
        David Rientjes <rientjes@google.com>, Ingo Molnar <mingo@elte.hu>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Eric Paris <eparis@redhat.com>,
        "Serge E. Hallyn" <serge.hallyn@canonical.com>,
        linux-doc@vger.kernel.org
Date: Tue, 24 Jan 2012 12:34:33 -0500
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On Mon, 2012-01-23 at 13:21 -0800, Kees Cook wrote:
> Add the "proc_pid_mem" sysctl to control whether or not /proc/pid/mem is
> allowed to work: 0: disabled, 1: read only, 2: read/write (default).

Both your git commit and the Documentation/ entry are totally missing a
rationale for this.  Why would an admin want to set this on or off?
What replaces it, if anything?  What are the tradeoffs with its
replacement?  What userspace programs might break when this is toggled?