linux-kernel - [PATCH 3.12 022/142] USB: serial: io_ti: fix information leak in completion handler

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Message-Id: <ef598b806384182a74f2aa9bc24a0284faf3940e.1491838390.git.jslaby@suse.cz>
Date:   Mon, 10 Apr 2017 17:31:43 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 022/142] USB: serial: io_ti: fix information leak in completion handler

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

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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>
---
 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 2e4589a7b982..e527a2780855 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -1658,7 +1658,7 @@ static void edge_bulk_in_callback(struct urb *urb)
 
 	port_number = edge_port->port->port_number;
 
-	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);
-- 
2.12.2