[SRU][Trusty][PATCH 1/1] x86/acpi: Prevent out of bound access caused by broken ACPI tables

[Kleber Sacilotto de Souza]

From: Seunghun Han <kkamagui at gmail.com>

The bus_irq argument of mp_override_legacy_irq() is used as the index into
the isa_irq_to_gsi[] array. The bus_irq argument originates from
ACPI_MADT_TYPE_IO_APIC and ACPI_MADT_TYPE_INTERRUPT items in the ACPI
tables, but is nowhere sanity checked.

That allows broken or malicious ACPI tables to overwrite memory, which
might cause malfunction, panic or arbitrary code execution.

Add a sanity check and emit a warning when that triggers.

[ tglx: Added warning and rewrote changelog ]

Signed-off-by: Seunghun Han <kkamagui at gmail.com>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Cc: security at kernel.org
Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
Cc: stable at vger.kernel.org
Signed-off-by: Ingo Molnar <mingo at kernel.org>

CVE-2017-11473
(cherry picked from commit dad5ab0db8deac535d03e3fe3d8f2892173fa6a4)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
---
 arch/x86/kernel/acpi/boot.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 6c0b43bd024b..2c3cd05ba747 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -918,6 +918,14 @@ void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger, u32 gsi)
 	int pin;
 	struct mpc_intsrc mp_irq;
 
+	/*
+	 * Check bus_irq boundary.
+	 */
+	if (bus_irq >= NR_IRQS_LEGACY) {
+		pr_warn("Invalid bus_irq %u for legacy override\n", bus_irq);
+		return;
+	}
+
 	/*
 	 * Convert 'gsi' to 'ioapic.pin'.
 	 */
-- 
2.17.1