linux-kernel - [PATCH 3.3.0-rc3] Fix use-after-free in acpi_map

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Message-ID: <20120216000643.GA7508@petr-dev3.eng.vmware.com>
Date:	Wed, 15 Feb 2012 16:06:43 -0800
From:	Petr Vandrovec <petr@...are.com>
To:	lenb@...nel.org
Cc:	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	akataria@...are.com, dcovelli@...are.com
Subject: [PATCH 3.3.0-rc3] Fix use-after-free in acpi_map_lsapic

From: Petr Vandrovec <petr@...are.com>

When processor is being hot-added to the system, acpi_map_lsapic invokes
ACPI _MAT method to find APIC ID and flags, verifies that returned structure
is indeed ACPI's local APIC structure, and that flags contain MADT_ENABLED
bit.  Then saves APIC ID, frees structure - and accesses structure when
computing arguments for acpi_register_lapic call.  Which sometime leads
to acpi_register_lapic call being made with second argument zero, failing
to bring processor online with error 'Unable to map lapic to logical cpu
number'.

As lapic->lapic_flags & ACPI_MADT_ENABLED was already confirmed to be non-zero
few lines above, we can just pass unconditional ACPI_MADT_ENABLED to the
acpi_register_lapic.

Thanks, Petr

Signed-off-by: Petr Vandrovec <petr@...are.com>
Signed-off-by: Alok Kataria <akataria@...are.com>

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index ce664f3..a4a0901 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -650,7 +650,7 @@ static int __cpuinit _acpi_map_lsapic(acpi_handle handle, int *pcpu)
 		goto free_tmp_map;

 	cpumask_copy(tmp_map, cpu_present_mask);
-	acpi_register_lapic(physid, lapic->lapic_flags & ACPI_MADT_ENABLED);
+	acpi_register_lapic(physid, ACPI_MADT_ENABLED);

 	/*
 	 * If mp_register_lapic successfully generates a new logical cpu
--
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