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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 5/6] proc: make check_mem_permission() return an mm_struct on success
In-Reply-To: <1299631343-4499-6-git-send-email-wilsons@start.ca>
References: <1299631343-4499-1-git-send-email-wilsons@start.ca> <1299631343-4499-6-git-send-email-wilsons@start.ca>
Message-Id: <20110309151900.0403.A69D9226@jp.fujitsu.com>
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Date: Wed,  9 Mar 2011 15:20:16 +0900 (JST)
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To: Stephen Wilson <wilsons@start.ca>
Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Rik van Riel <riel@redhat.com>, Roland McGrath <roland@redhat.com>, Matt Mackall <mpm@selenic.com>, David Rientjes <rientjes@google.com>, Nick Piggin <npiggin@kernel.dk>, Andrea Arcangeli <aarcange@redhat.com>, Mel Gorman <mel@csn.ul.ie>, Ingo Molnar <mingo@elte.hu>, Michel Lespinasse <walken@google.com>, Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org

> This change allows us to take advantage of access_remote_vm(), which in turn
> enables a secure mem_write() implementation.
> 
> The previous implementation of mem_write() was insecure since the target task
> could exec a setuid-root binary between the permission check and the actual
> write.  Holding a reference to the target mm_struct eliminates this
> vulnerability.
> 
> Signed-off-by: Stephen Wilson <wilsons@start.ca>

OK, I like this idea. So, I suppose you will resend newer version as applied Al's
comment and I'll be able to ack this.

Thanks.



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