Re: [PATCH] of: Fix comparison of reserved memory regions

On Sat, Dec 5, 2015 at 5:43 AM, Michael Ellerman [off-list ref] wrote:

On 5 December 2015 04:07:39 GMT+11:00, Mitchel Humpherys [off-list ref] wrote:

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On Wed, Nov 18 2015 at 09:46:38 PM, Michael Ellerman
[off-list ref] wrote:

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In order to check for overlapping reserved memory regions, we first

need

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to sort the array of memory regions. This is implemented using

sort(),

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and a custom comparison function __rmem_cmp().

Unfortunatley __rmem_cmp() doesn't work in all cases. Because the two
base values are phys_addr_t, they may be u64 on some platforms, in

which

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case subtracting one from the other and then (implicitly) casting to

int

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does not give us the -ve/0/+ve value we need.

This leads to incorrect reports about overlaps, eg:

  ibm,slw-image@1ffe600000 (0x0000001ffe600000--0x0000001ffe700000)

overlaps with

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  ibm,firmware-allocs-memory@1000000000

(0x0000001000000000--0x0000001000dc0200)

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Fix it by just doing the standard double if and return 0 logic.

Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory

regions")

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Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
 drivers/of/of_reserved_mem.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Woops, thanks.

Tested-by: Mitchel Humpherys <redacted>

Thanks for testing.

Rob, can we get this merged for 4.4 please?

Yes. I meant to last week, but was waiting on getting another issue
sorted out. I should get it to Linus in the next couple of days.

Rob