From 691a03cfe8ca483f9c48153b869d354e4ae3abef Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Tue, 21 Aug 2018 11:59:52 +0200
Subject: [PATCH] USB: serial: io_ti: fix array underflow in completion handler
Git-commit: 691a03cfe8ca483f9c48153b869d354e4ae3abef
Patch-mainline: v4.19-rc4
References: bsc#1051510

As reported by Dan Carpenter, a malicious USB device could set
port_number to a negative value and we would underflow the port array in
the interrupt completion handler.

As these devices only have one or two ports, fix this by making sure we
only consider the seventh bit when determining the port number (and
ignore bits 0xb0 which are typically set to 0x30).

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/usb/serial/io_ti.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/serial/io_ti.h b/drivers/usb/serial/io_ti.h
index e53c68261017..9bbcee37524e 100644
--- a/drivers/usb/serial/io_ti.h
+++ b/drivers/usb/serial/io_ti.h
@@ -173,7 +173,7 @@ struct ump_interrupt {
 }  __attribute__((packed));
 
 
-#define TIUMP_GET_PORT_FROM_CODE(c)	(((c) >> 4) - 3)
+#define TIUMP_GET_PORT_FROM_CODE(c)	(((c) >> 6) & 0x01)
 #define TIUMP_GET_FUNC_FROM_CODE(c)	((c) & 0x0f)
 #define TIUMP_INTERRUPT_CODE_LSR	0x03
 #define TIUMP_INTERRUPT_CODE_MSR	0x04
-- 
2.18.0