linux-kernel - Re: [PATCH] mm: fix unmap

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Message-ID: <1308902029.27849.16.camel@twins>
Date:	Fri, 24 Jun 2011 09:53:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Chuck Ebbert <cebbert@...hat.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] mm: fix unmap_atomic range checks

On Fri, 2011-06-24 at 02:53 -0400, Chuck Ebbert wrote:
> Commit 3e4d3af501cccdc8a8cca41bdbe57d54ad7e7e73 ("mm: stack based
> kmap_atomic()", in 2.6.37-rc1) had three places where range checking
> logic was reversed.

Where's the oopses to go along with this?

I think its actually correct, since on both x86 and tile we have:

#define __fix_to_virt(x)        (FIXADDR_TOP - ((x) << PAGE_SHIFT))

Which flips the address space around, ie, END < BEGIN.        

> Signed-off-by: Chuck Ebbert <cebbert@...hat.com>
> 
> --- a/arch/tile/mm/highmem.c
> +++ b/arch/tile/mm/highmem.c
> @@ -235,8 +235,8 @@ void __kunmap_atomic(void *kvaddr)
>  {
>  	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
>  
> -	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
> -	    vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
> +	if (vaddr >= __fix_to_virt(FIX_KMAP_BEGIN) &&
> +	    vaddr <= __fix_to_virt(FIX_KMAP_END)) {
>  		pte_t *pte = kmap_get_pte(vaddr);
>  		pte_t pteval = *pte;
>  		int idx, type;
> --- a/arch/x86/mm/highmem_32.c
> +++ b/arch/x86/mm/highmem_32.c
> @@ -70,8 +70,8 @@ void __kunmap_atomic(void *kvaddr)
>  {
>  	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
>  
> -	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
> -	    vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
> +	if (vaddr >= __fix_to_virt(FIX_KMAP_BEGIN) &&
> +	    vaddr <= __fix_to_virt(FIX_KMAP_END)) {
>  		int idx, type;
>  
>  		type = kmap_atomic_idx();
> --- a/arch/x86/mm/iomap_32.c
> +++ b/arch/x86/mm/iomap_32.c
> @@ -94,8 +94,8 @@ iounmap_atomic(void __iomem *kvaddr)
>  {
>  	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
>  
> -	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
> -	    vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
> +	if (vaddr >= __fix_to_virt(FIX_KMAP_BEGIN) &&
> +	    vaddr <= __fix_to_virt(FIX_KMAP_END)) {
>  		int idx, type;
>  
>  		type = kmap_atomic_idx();

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