linux-kernel - Re: [PATCH 4.4 33/35] nfit, libnvdimm: fix interleave set cookie calculation

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Date:   Sun, 19 Mar 2017 16:38:36 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Nicholas Moulin <nicholas.w.moulin@...ux.intel.com>
Subject: Re: [PATCH 4.4 33/35] nfit, libnvdimm: fix interleave set cookie
 calculation

On Thu, 2017-03-16 at 23:29 +0900, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dan Williams <dan.j.williams@...el.com>
> 
> commit 86ef58a4e35e8fa66afb5898cf6dec6a3bb29f67 upstream.
> 
> The interleave-set cookie is a sum that sanity checks the composition of
> an interleave set has not changed from when the namespace was initially
> created.  The checksum is calculated by sorting the DIMMs by their
> location in the interleave-set. The comparison for the sort must be
> 64-bit wide, not byte-by-byte as performed by memcmp() in the broken
> case.
[...]
> --- a/drivers/acpi/nfit.c
> +++ b/drivers/acpi/nfit.c
[...]
> +static int cmp_map(const void *m0, const void *m1)
> +{
> +	const struct nfit_set_info_map *map0 = m0;
> +	const struct nfit_set_info_map *map1 = m1;
> +
> +	return map0->region_offset - map1->region_offset;
> +}
[...]

This is returning an int, thus it's effectively doing a 32-bit
comparison and not the 64-bit comparison you say is needed.

I think this function needs to do something like:

	return (map0->region_offset < map1->region_offset) ? -1 :
		(map0->region_offset == map1->region_offset) ? 0 : 1;

Ben.

-- 
Ben Hutchings
Power corrupts.  Absolute power is kind of neat.
                           - John Lehman, Secretary of the US Navy
1981-1987

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