linux-kernel - Re: [PATCH] mm: Check we have the right vma in __access_remote

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Message-Id: <20110411165035.5a303647.akpm@linux-foundation.org>
Date:	Mon, 11 Apr 2011 16:50:35 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<hughd@...gle.com>, <walken@...gle.com>, <aarcange@...hat.com>,
	<riel@...hat.com>, <linuxppc-dev@...abs.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH] mm: Check we have the right vma in __access_remote_vm()

On Fri,  8 Apr 2011 17:24:01 +1000 (EST)
Michael Ellerman <michael@...erman.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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