linux-kernel - [PATCH 3.10 168/250] USB: serial: io_ti: fix information leak in completion handler

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Message-Id: <1496876436-32402-169-git-send-email-w@1wt.eu>
Date:   Thu,  8 Jun 2017 00:59:14 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Johan Hovold <johan@...nel.org>, Jiri Slaby <jslaby@...e.cz>,
        Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 168/250] USB: serial: io_ti: fix information leak in completion handler

From: Johan Hovold <johan@...nel.org>

commit 654b404f2a222f918af9b0cd18ad469d0c941a8e upstream.

Add missing sanity check to the bulk-in completion handler to avoid an
integer underflow that can be triggered by a malicious device.

This avoids leaking 128 kB of memory content from after the URB transfer
buffer to user space.

Fixes: 8c209e6782ca ("USB: make actual_length in struct urb field u32")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/usb/serial/io_ti.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index e2dc182..20814d5 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -1661,7 +1661,7 @@ static void edge_bulk_in_callback(struct urb *urb)
 
 	port_number = edge_port->port->number - edge_port->port->serial->minor;
 
-	if (edge_port->lsr_event) {
+	if (urb->actual_length > 0 && edge_port->lsr_event) {
 		edge_port->lsr_event = 0;
 		dev_dbg(dev, "%s ===== Port %u LSR Status = %02x, Data = %02x ======\n",
 			__func__, port_number, edge_port->lsr_mask, *data);
-- 
2.8.0.rc2.1.gbe9624a