From 70ac67826602edf8c0ccb413e5ba7eacf597a60c Mon Sep 17 00:00:00 2001
From: Seunghun Han <kkamagui@gmail.com>
Date: Tue, 18 Jul 2017 20:03:51 +0900
Subject: x86/acpi: Prevent out of bound access caused by broken ACPI tables
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@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: security@kernel.org
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: stable@vger.kernel.org
---
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 6bb6806..7491e73 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -347,6 +347,14 @@ static void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
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'.
*/
ioapic = mp_find_ioapic(gsi);
--
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