Date: Mon, 11 Apr 2011 16:50:35 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Michael Ellerman <michael@ellerman.id.au>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>, <hughd@google.com>,
        <walken@google.com>, <aarcange@redhat.com>, <riel@redhat.com>,
        <linuxppc-dev@ozlabs.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] mm: Check we have the right vma in __access_remote_vm()
Message-Id: <20110411165035.5a303647.akpm@linux-foundation.org>
In-Reply-To: <10e5cbf67c850b6ae511979bdbad1761236ad9b0.1302247435.git.michael@ellerman.id.au>
References: <10e5cbf67c850b6ae511979bdbad1761236ad9b0.1302247435.git.michael@ellerman.id.au>
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On Fri,  8 Apr 2011 17:24:01 +1000 (EST)
Michael Ellerman <michael@ellerman.id.au> wrote:

> In __access_remote_vm() we need to check that we have found the right
> vma, not the following vma, before we try to access it. Otherwise we
> might call the vma's access routine with an address which does not
> fall inside the vma.
> 

hm, mysteries.  Does this patch fix any known problem in any known
kernel, or was the problem discovered by inspection, or what?

> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 9da8cab..ce999ca 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3678,7 +3678,7 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
>  			 */
>  #ifdef CONFIG_HAVE_IOREMAP_PROT
>  			vma = find_vma(mm, addr);
> -			if (!vma)
> +			if (!vma || vma->vm_start > addr)
>  				break;
>  			if (vma->vm_ops && vma->vm_ops->access)
>  				ret = vma->vm_ops->access(vma, addr, buf,
--
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