linux-kernel - Re: [PATCH v3 4/5] x86: fix memory corruption in acpi_unmap

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Message-ID: <20140414092047.GC19771@gmail.com>
Date:	Mon, 14 Apr 2014 11:20:47 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Igor Mammedov <imammedo@...hat.com>
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, bp@...e.de,
	paul.gortmaker@...driver.com, JBeulich@...e.com, prarit@...hat.com,
	drjones@...hat.com, toshi.kani@...com, riel@...hat.com,
	gong.chen@...ux.intel.com, andi@...stfloor.org, lenb@...nel.org,
	rjw@...ysocki.net, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 4/5] x86: fix memory corruption in acpi_unmap_lsapic()


* Igor Mammedov <imammedo@...hat.com> wrote:

> if during CPU hotplug master CPU failed to wake up AP
> it set percpu x86_cpu_to_apicid to BAD_APICID=0xFFFF for AP.
> 
> However following attempt to unplug that CPU will lead to
> out of bound write access to __apicid_to_node[] which is
> 32768 items long on x86_64 kernel.
> 
> So drop setting x86_cpu_to_apicid to BAD_APICID in do_boot_cpu()
> and allow acpi_processor_remove()->acpi_unmap_lsapic() cleanly
> remove CPU.

Same suggestion as for the other fix patch: the fix should precede the 
patch that exposes it.

Thanks,

	Ingo
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