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[PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only property

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  [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only property Marc Zyngier <marc.zyngier@arm.com> - 2015-08-14 16:50 +0200
    Re: [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only  property Bjorn Helgaas <bhelgaas@google.com> - 2015-08-14 17:00 +0200
      Re: [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only  property Marc Zyngier <marc.zyngier@arm.com> - 2015-08-14 17:50 +0200

#1207566 — [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only property

When find_and_init_phbs() looks for the probe-only property, it seems
to trust the firmware to be correctly written, and assumes that there
is a parameter to the property.

It is conceivable that the firmware could not be that perfect, and it
could expose this property naked (at least one arm64 platform seems to
exhibit this exact behaviour). The setup code the ends up making
a decision based on whatever the property pointer points to, which
is likely to be junk.

Instead, let's check for the validity of the property, and ignore
it if the firmware couldn't make up its mind.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 arch/powerpc/platforms/pseries/setup.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index df6a704..6bdc1f9 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -490,14 +490,19 @@ static void __init find_and_init_phbs(void)
 	 */
 	if (of_chosen) {
 		const int *prop;
+		int len;
 
 		prop = of_get_property(of_chosen,
-				"linux,pci-probe-only", NULL);
+				"linux,pci-probe-only", &len);
 		if (prop) {
-			if (*prop)
-				pci_add_flags(PCI_PROBE_ONLY);
-			else
-				pci_clear_flags(PCI_PROBE_ONLY);
+			if (len) {
+				if (be32_to_cpup(prop))
+					pci_add_flags(PCI_PROBE_ONLY);
+				else
+					pci_clear_flags(PCI_PROBE_ONLY);
+			} else {
+				pr_warn("linux,pci-probe-only set without value, ignoring\n");
+			}
 		}
 	}
 }
-- 
2.1.4

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#1207571 — Re: [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only property

Hi Marc,

On Fri, Aug 14, 2015 at 03:41:07PM +0100, Marc Zyngier wrote:
> When find_and_init_phbs() looks for the probe-only property, it seems
> to trust the firmware to be correctly written, and assumes that there
> is a parameter to the property.
> 
> It is conceivable that the firmware could not be that perfect, and it
> could expose this property naked (at least one arm64 platform seems to
> exhibit this exact behaviour). The setup code the ends up making
> a decision based on whatever the property pointer points to, which
> is likely to be junk.
> 
> Instead, let's check for the validity of the property, and ignore
> it if the firmware couldn't make up its mind.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/powerpc/platforms/pseries/setup.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
> index df6a704..6bdc1f9 100644
> --- a/arch/powerpc/platforms/pseries/setup.c
> +++ b/arch/powerpc/platforms/pseries/setup.c
> @@ -490,14 +490,19 @@ static void __init find_and_init_phbs(void)
>  	 */
>  	if (of_chosen) {
>  		const int *prop;
> +		int len;
>  
>  		prop = of_get_property(of_chosen,
> -				"linux,pci-probe-only", NULL);
> +				"linux,pci-probe-only", &len);
>  		if (prop) {
> -			if (*prop)
> -				pci_add_flags(PCI_PROBE_ONLY);
> -			else
> -				pci_clear_flags(PCI_PROBE_ONLY);
> +			if (len) {
> +				if (be32_to_cpup(prop))
> +					pci_add_flags(PCI_PROBE_ONLY);
> +				else
> +					pci_clear_flags(PCI_PROBE_ONLY);
> +			} else {
> +				pr_warn("linux,pci-probe-only set without value, ignoring\n");
> +			}

This seems essentially identical to the pci-host-generic version.
Is there a way we can factor it out so there's only one copy?

>  		}
>  	}
>  }
> -- 
> 2.1.4
> 
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#1207581 — Re: [PATCH 2/3] powerpc: PCI: Fix lookup of linux,pci-probe-only property

Hi Bjorn,

On 14/08/15 15:57, Bjorn Helgaas wrote:
> Hi Marc,
> 
> On Fri, Aug 14, 2015 at 03:41:07PM +0100, Marc Zyngier wrote:
>> When find_and_init_phbs() looks for the probe-only property, it seems
>> to trust the firmware to be correctly written, and assumes that there
>> is a parameter to the property.
>>
>> It is conceivable that the firmware could not be that perfect, and it
>> could expose this property naked (at least one arm64 platform seems to
>> exhibit this exact behaviour). The setup code the ends up making
>> a decision based on whatever the property pointer points to, which
>> is likely to be junk.
>>
>> Instead, let's check for the validity of the property, and ignore
>> it if the firmware couldn't make up its mind.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>> ---
>>  arch/powerpc/platforms/pseries/setup.c | 15 ++++++++++-----
>>  1 file changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
>> index df6a704..6bdc1f9 100644
>> --- a/arch/powerpc/platforms/pseries/setup.c
>> +++ b/arch/powerpc/platforms/pseries/setup.c
>> @@ -490,14 +490,19 @@ static void __init find_and_init_phbs(void)
>>  	 */
>>  	if (of_chosen) {
>>  		const int *prop;
>> +		int len;
>>  
>>  		prop = of_get_property(of_chosen,
>> -				"linux,pci-probe-only", NULL);
>> +				"linux,pci-probe-only", &len);
>>  		if (prop) {
>> -			if (*prop)
>> -				pci_add_flags(PCI_PROBE_ONLY);
>> -			else
>> -				pci_clear_flags(PCI_PROBE_ONLY);
>> +			if (len) {
>> +				if (be32_to_cpup(prop))
>> +					pci_add_flags(PCI_PROBE_ONLY);
>> +				else
>> +					pci_clear_flags(PCI_PROBE_ONLY);
>> +			} else {
>> +				pr_warn("linux,pci-probe-only set without value, ignoring\n");
>> +			}
> 
> This seems essentially identical to the pci-host-generic version.
> Is there a way we can factor it out so there's only one copy?

Probably. drivers/of/of_pci.c seems like a good landing place for it.
I'll hack something and repost it.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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