linux-kernel - Re: [PATCH 5/6] proc: use task_access_lock() instead of ptrace_may

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Message-ID: <4F86D702.30209@gmail.com>
Date:	Thu, 12 Apr 2012 21:22:10 +0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH 5/6] proc: use task_access_lock() instead of ptrace_may_access()

On 04/11/2012 01:59 PM, Cong Wang wrote:
> There are several places in fs/proc/base.c still use ptrace_may_access()
> directly to check the permission, actually this just gets a snapshot of
> the permission, nothing prevents the target task from raising the priviledges
> itself, it is better to use task_access_lock() for these places, to hold
> the priviledges.
>
Hi, Andrew,

Please drop this patch, it introduces a deadlock when execve() a 
/proc/<pid>/exec file, and it is not a big improvement nor fixes any 
bugs, so let's just drop this one.

Thanks!
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