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

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Message-ID: <BANLkTi=RJ2GHvHQ3mZiQ-L-MTVUQH-V-eA@mail.gmail.com>
Date:	Mon, 4 Apr 2011 23:42:54 -0700
From:	Michel Lespinasse <walken@...gle.com>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, hughd@...gle.com,
	aarcange@...hat.com, riel@...hat.com,
	Andrew Morton <akpm@...l.org>, linuxppc-dev@...abs.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH] mm: Check we have the right vma in access_process_vm()

On Mon, Apr 4, 2011 at 11:24 PM, Michael Ellerman
<michael@...erman.id.au> wrote:
> In access_process_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.
>
> Signed-off-by: Michael Ellerman <michael@...erman.id.au>

Please note that the code has moved into __access_remote_vm() in
current linus tree. Also, should len be truncated before calling
vma->vm_ops->access() so that we can guarantee it won't overflow past
the end of the vma ?

> diff --git a/mm/memory.c b/mm/memory.c
> index 5823698..7e6f17b 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3619,7 +3619,7 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
>                         */
>  #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,
> --
> 1.7.1

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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