Re: [PATCH] time: Cast tv_nsec to u64 for proper shifting in update_vsyscall()

[H. Peter Anvin]

On 05/09/2014 08:11 AM, Boris Ostrovsky wrote:
> With tk->wall_to_monotonic.tv_nsec being a 32-bit value on 32-bit
> systems, (tk->wall_to_monotonic.tv_nsec << tk->shift) in update_vsyscall()
> may lose upper bits or, worse, add them since compiler will do this:
> 	(u64)(tk->wall_to_monotonic.tv_nsec << tk->shift)
> instead of
> 	((u64)tk->wall_to_monotonic.tv_nsec << tk->shift)
> 
> So if, for example, tv_nsec is 0x800000 and shift is 8 we will end up
> with 0xffffffff80000000 instead of 0x80000000. And then we are stuck in
> the subsequent 'while' loop.
> 
> We need explicit cast.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

This is needed in stable only for v3.14, right?

	-hpa


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