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From: Rusty Russell <rusty@rustcorp.com.au>
To: David John <davidjon@xenontk.org>
Subject: Re: [PATCH v2] Check the node argument passed to cpumask_of_node
Date: Mon, 4 Jan 2010 14:58:22 +1030
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On Sat, 2 Jan 2010 04:45:47 pm David John wrote:
> Commit e0cd516 "PCI: derive nearby CPUs from device's instead of bus' NUMA information"
> causes an null pointer dereference when reading from the sysfs attributes local_cpu*
> on Intel machines with no ACPI NUMA proximity info, since dev->numa_node gets set to -1
> for all PCI devices, which then gets passed to cpumask_of_node.
> 
> Ensure that the node value is valid.

This only works for x86, and only for !CONFIG_DEBUG_PER_CPU_MAPS.

I suggest fixing the callers introduced in e0cd516 for the moment,
then if you feel enthused, change the semantics of cpumask_of_node and
remove the checks from the various callers.

(And please only check for -1: it has a special meaning, unlike other
invalid numbers which indicate a bug).

Thanks,
Rusty.