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
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 6bb680671088694af194eabd987fc86b2b02441d..7491e73d92530bf868a9b91b2c71c892bcbdb94a 100644 (file)
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -346,6 +346,14 @@ static void __init mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
        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'.
         */