[GIT PULL] Cacheflush updates for 3.12

[Will Deacon]

Hi guys,

I was out-of-office yesterday, so sorry for the radio silence.

On Thu, Dec 05, 2013 at 03:14:31PM +0000, Jon Medhurst (Tixy) wrote:
> On Thu, 2013-12-05 at 14:23 +0000, Jon Medhurst (Tixy) wrote:
> > On Wed, 2013-12-04 at 16:13 +0000, Will Deacon wrote:
> > > took another look at that patch and can't see anything obviously wrong
> > > with it. 
> > 
> > If the memory region isn't guaranteed to be page aligned then doesn't it
> > flush up to PAGE_SIZE-1 more bytes than requested and so exceed the
> > bounds check in do_cache_op? Fixing this as below _appears_ to stop the
> > Browser crashes I'm seeing (still doing some more testing)...

Well spotted! We used to round down to a page, but I fixed that in the same
series and didn't notice I'd introduce a bug here. Thanks for digging.

Interesting that we've not heard more reports of this...

> Actually, a smaller patch and one which avoids the possibility of
> arithmetic owerflow is... 
> 
> From: Jon Medhurst <tixy at linaro.org>
> Date: Thu, 5 Dec 2013 14:29:24 +0000
> Subject: [PATCH] ARM: cacheflush: correctly limit range of memory region
>  being flushed
> 
> The __do_cache_op function operates with a 'chunk' size of one page
> but fails to limit the size of the final chunk so as to not exceed
> the specified memory region. Fix this.
> 
> Signed-off-by: Jon Medhurst <tixy at linaro.org>
> ---
>  arch/arm/kernel/traps.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> index dbf0923..7940241 100644
> --- a/arch/arm/kernel/traps.c
> +++ b/arch/arm/kernel/traps.c
> @@ -509,9 +509,10 @@ static inline int
>  __do_cache_op(unsigned long start, unsigned long end)
>  {
>  	int ret;
> -	unsigned long chunk = PAGE_SIZE;
>  
>  	do {
> +		unsigned long chunk = min(PAGE_SIZE, end - start);
> +
>  		if (signal_pending(current)) {
>  			struct thread_info *ti = current_thread_info();

  Acked-by: Will Deacon <will.deacon at arm.com>

Please can you put this into the patch system, along with a CC stable?

Cheers,

Will