linux-kernel - [PATCH 4.19 10/16] comedi: ni_usb6501: fix NULL-deref in command paths

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Message-Id: <20211110182002.319464581@linuxfoundation.org>
Date:   Wed, 10 Nov 2021 19:43:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Luca Ellero <luca.ellero@...ckedbrain.com>,
        Ian Abbott <abbotti@....co.uk>, Johan Hovold <johan@...nel.org>
Subject: [PATCH 4.19 10/16] comedi: ni_usb6501: fix NULL-deref in command paths

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

commit 907767da8f3a925b060c740e0b5c92ea7dbec440 upstream.

The driver uses endpoint-sized USB transfer buffers but had no sanity
checks on the sizes. This can lead to zero-size-pointer dereferences or
overflowed transfer buffers in ni6501_port_command() and
ni6501_counter_command() if a (malicious) device has smaller max-packet
sizes than expected (or when doing descriptor fuzz testing).

Add the missing sanity checks to probe().

Fixes: a03bb00e50ab ("staging: comedi: add NI USB-6501 support")
Cc: stable@...r.kernel.org      # 3.18
Cc: Luca Ellero <luca.ellero@...ckedbrain.com>
Reviewed-by: Ian Abbott <abbotti@....co.uk>
Signed-off-by: Johan Hovold <johan@...nel.org>
Link: https://lore.kernel.org/r/20211027093529.30896-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/staging/comedi/drivers/ni_usb6501.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/drivers/staging/comedi/drivers/ni_usb6501.c
+++ b/drivers/staging/comedi/drivers/ni_usb6501.c
@@ -144,6 +144,10 @@ static const u8 READ_COUNTER_RESPONSE[]
 					   0x00, 0x00, 0x00, 0x02,
 					   0x00, 0x00, 0x00, 0x00};
 
+/* Largest supported packets */
+static const size_t TX_MAX_SIZE	= sizeof(SET_PORT_DIR_REQUEST);
+static const size_t RX_MAX_SIZE	= sizeof(READ_PORT_RESPONSE);
+
 enum commands {
 	READ_PORT,
 	WRITE_PORT,
@@ -501,6 +505,12 @@ static int ni6501_find_endpoints(struct
 	if (!devpriv->ep_rx || !devpriv->ep_tx)
 		return -ENODEV;
 
+	if (usb_endpoint_maxp(devpriv->ep_rx) < RX_MAX_SIZE)
+		return -ENODEV;
+
+	if (usb_endpoint_maxp(devpriv->ep_tx) < TX_MAX_SIZE)
+		return -ENODEV;
+
 	return 0;
 }