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From: Willy Tarreau <w@1wt.eu>
Newsgroups: linux.kernel
Subject: [PATCH 3.10 045/250] USB: serial: io_ti: fix another NULL-deref at open
Date: Thu, 08 Jun 2017 01:10:03 +0200
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From: Johan Hovold <johan@kernel.org>

commit 4f9785cc99feeb3673993b471f646b4dbaec2cc1 upstream.

In case a device is left in "boot-mode" we must not register any port
devices in order to avoid a NULL-pointer dereference on open due to
missing endpoints. This could be used by a malicious device to trigger
an OOPS:

Unable to handle kernel NULL pointer dereference at virtual address 00000030
...
[<bf0caa84>] (edge_open [io_ti]) from [<bf0b0118>] (serial_port_activate+0x68/0x98 [usbserial])
[<bf0b0118>] (serial_port_activate [usbserial]) from [<c0470ca4>] (tty_port_open+0x9c/0xe8)
[<c0470ca4>] (tty_port_open) from [<bf0b0da0>] (serial_open+0x48/0x6c [usbserial])
[<bf0b0da0>] (serial_open [usbserial]) from [<c0469178>] (tty_open+0xcc/0x5cc)

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
 drivers/usb/serial/io_ti.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index fa0ca9e..e1b3e79 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -1402,7 +1402,7 @@ stayinbootmode:
 	dev_dbg(dev, "%s - STAYING IN BOOT MODE\n", __func__);
 	serial->product_info.TiMode = TI_MODE_BOOT;
 
-	return 0;
+	return 1;
 }
 
 
@@ -2451,11 +2451,14 @@ static int edge_startup(struct usb_serial *serial)
 	usb_set_serial_data(serial, edge_serial);
 
 	status = download_fw(edge_serial);
-	if (status) {
+	if (status < 0) {
 		kfree(edge_serial);
 		return status;
 	}
 
+	if (status > 0)
+		return 1;	/* bind but do not register any ports */
+
 	return 0;
 }
 
-- 
2.8.0.rc2.1.gbe9624a