[PATCH] arch/x86/kernel/acpi/boot: fix buffer overflow on negative index in mp_config_acpi_gsi()

[Alexander Sapozhnikov]

Variable 'ioapic', which may receive negative value by calling 
function 'mp_find_ioapic' at boot.c:465, is used at
io_apic.c:128 by passing as 1st parameter to function 'mpc_ioapic_id' 
at boot.c:466

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Alexander Sapozhnikov <alsp705@xxxxxxxxx>
---
 arch/x86/kernel/acpi/boot.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 907cc98b1938..abb78822f164 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -463,8 +463,10 @@ static void mp_config_acpi_gsi(struct device *dev, u32 gsi, int trigger,
 	mp_irq.srcbus = number;
 	mp_irq.srcbusirq = (((devfn >> 3) & 0x1f) << 2) | ((pin - 1) & 3);
 	ioapic = mp_find_ioapic(gsi);
-	mp_irq.dstapic = mpc_ioapic_id(ioapic);
-	mp_irq.dstirq = mp_find_ioapic_pin(ioapic, gsi);
+	if (ioapic >= 0) {
+		mp_irq.dstapic = mpc_ioapic_id(ioapic);
+		mp_irq.dstirq = mp_find_ioapic_pin(ioapic, gsi);
+	}
 
 	mp_save_irq(&mp_irq);
 #endif
-- 
2.34.1