[PATCH] of: Fix comparison of reserved memory regions

[PATCH] of: Fix comparison of reserved memory regions

[Michael Ellerman]

In order to check for overlapping reserved memory regions, we first need
to sort the array of memory regions. This is implemented using sort(),
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
case subtracting one from the other and then (implicitly) casting to int
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
  ibm,firmware-allocs-memory@1000000000 (0x0000001000000000--0x0000001000dc0200)

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

Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory regions")
Signed-off-by: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
---
 drivers/of/of_reserved_mem.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index be77e75c587d..1a3556a9e9ea 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -206,7 +206,13 @@ static int __init __rmem_cmp(const void *a, const void *b)
 {
 	const struct reserved_mem *ra = a, *rb = b;
 
-	return ra->base - rb->base;
+	if (ra->base < rb->base)
+		return -1;
+
+	if (ra->base > rb->base)
+		return 1;
+
+	return 0;
 }
 
 static void __init __rmem_check_for_overlap(void)
-- 
2.5.0

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

[Mitchel Humpherys]

On Wed, Nov 18 2015 at 09:46:38 PM, Michael Ellerman <mpe@ellerman.id.au> wrote:
> In order to check for overlapping reserved memory regions, we first need
> to sort the array of memory regions. This is implemented using sort(),
> 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
> case subtracting one from the other and then (implicitly) casting to int
> 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
>   ibm,firmware-allocs-memory@1000000000 (0x0000001000000000--0x0000001000dc0200)
>
> Fix it by just doing the standard double if and return 0 logic.
>
> Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory regions")
> 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 <mitchelh@codeaurora.org>

-Mitch

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The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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

[Michael Ellerman]

On 5 December 2015 04:07:39 GMT+11:00, Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> wrote:
>On Wed, Nov 18 2015 at 09:46:38 PM, Michael Ellerman
><mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org> wrote:
>> In order to check for overlapping reserved memory regions, we first
>need
>> to sort the array of memory regions. This is implemented using
>sort(),
>> 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
>> case subtracting one from the other and then (implicitly) casting to
>int
>> 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
>>   ibm,firmware-allocs-memory@1000000000
>(0x0000001000000000--0x0000001000dc0200)
>>
>> Fix it by just doing the standard double if and return 0 logic.
>>
>> Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory
>regions")
>> Signed-off-by: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
>> ---
>>  drivers/of/of_reserved_mem.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>
>Woops, thanks.
>
>Tested-by: Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

Thanks for testing.

Rob, can we get this merged for 4.4 please?

cheers 

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

[Rob Herring]

On Sat, Dec 5, 2015 at 5:43 AM, Michael Ellerman <michael-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org> wrote:
>
>
> On 5 December 2015 04:07:39 GMT+11:00, Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> wrote:
>>On Wed, Nov 18 2015 at 09:46:38 PM, Michael Ellerman
>><mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org> wrote:
>>> In order to check for overlapping reserved memory regions, we first
>>need
>>> to sort the array of memory regions. This is implemented using
>>sort(),
>>> 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
>>> case subtracting one from the other and then (implicitly) casting to
>>int
>>> 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
>>>   ibm,firmware-allocs-memory@1000000000
>>(0x0000001000000000--0x0000001000dc0200)
>>>
>>> Fix it by just doing the standard double if and return 0 logic.
>>>
>>> Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory
>>regions")
>>> Signed-off-by: Michael Ellerman <mpe-Gsx/Oe8HsFggBc27wqDAHg@public.gmane.org>
>>> ---
>>>  drivers/of/of_reserved_mem.c | 8 +++++++-
>>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>>Woops, thanks.
>>
>>Tested-by: Mitchel Humpherys <mitchelh-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
>
> 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
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Re: [PATCH] of: Fix comparison of reserved memory regions

[Michael Ellerman]

On Sun, 2015-12-06 at 14:31 -0600, Rob Herring wrote:
> On Sat, Dec 5, 2015 at 5:43 AM, Michael Ellerman <michael@ellerman.id.au> wrote:
> > On 5 December 2015 04:07:39 GMT+11:00, Mitchel Humpherys <mitchelh@codeaurora.org> wrote:
> > > On Wed, Nov 18 2015 at 09:46:38 PM, Michael Ellerman
> > > <mpe@ellerman.id.au> wrote:
> > > > Fix it by just doing the standard double if and return 0 logic.
> > > > 
> > > > Fixes: ae1add247bf8 ("of: Check for overlap in reserved memory
> > > regions")
> > > 
> > > Woops, thanks.
> > > 
> > > Tested-by: Mitchel Humpherys <mitchelh@codeaurora.org>
> > 
> > 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.

Sure thing. No great rush but would be nice for it to be fixed before 4.4
releases.

cheers