Date: Mon, 28 Nov 2005 22:02:11 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: Andrew Morton <akpm@osdl.org>, Linus Torvalds <torvalds@osdl.org>,
       linux-kernel@vger.kernel.org
Subject: Re: Fix crash when ptrace poking hugepage areas
Message-ID: <20051129060211.GB2240@holomorphy.com>
References: <20051129050628.GB12498@localhost.localdomain>
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On Tue, Nov 29, 2005 at 04:06:28PM +1100, David Gibson wrote:
> Bill, does this look like the correct fix for the problem to you?  If
> so, please apply Andrew.
> set_page_dirty() will not cope with being handed a page * which is
> part of a compound page, but not the master page in that compound
> page.  This case can occur via access_process_vm() if you attempt to
> write to another process's hugepage memory area using ptrace()
> (causing an oops or hang).
> This patch fixes the bug by first resolving the page * to the compound
> page's master page.
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

akpm had already responded, but my general response would have been
"Why on earth would you mark a hugepage dirty?" or similar.


-- wli
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