linux-kernel - [PATCH 3.16 037/134] [media] cx231xx-audio: fix NULL-deref at probe

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Message-ID: <lsq.1503062000.442166861@decadent.org.uk>
Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Mauro Carvalho Chehab" <mchehab@...pensource.com>,
        "Sri Deevi" <Srinivasa.Deevi@...exant.com>,
        "Hans Verkuil" <hans.verkuil@...co.com>,
        "Johan Hovold" <johan@...nel.org>
Subject: [PATCH 3.16 037/134] [media] cx231xx-audio: fix NULL-deref at probe

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 65f921647f4c89a2068478c89691f39b309b58f7 upstream.

Make sure to check the number of endpoints to avoid dereferencing a
NULL-pointer or accessing memory beyond the endpoint array should a
malicious device lack the expected endpoints.

Fixes: e0d3bafd0258 ("V4L/DVB (10954): Add cx231xx USB driver")

Cc: Sri Deevi <Srinivasa.Deevi@...exant.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/media/usb/cx231xx/cx231xx-audio.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- a/drivers/media/usb/cx231xx/cx231xx-audio.c
+++ b/drivers/media/usb/cx231xx/cx231xx-audio.c
@@ -699,6 +699,11 @@ static int cx231xx_audio_init(struct cx2
 					    hs_config_info[0].interface_info.
 					    audio_index + 1];
 
+	if (uif->altsetting[0].desc.bNumEndpoints < isoc_pipe + 1) {
+		err = -ENODEV;
+		goto err_free_card;
+	}
+
 	adev->end_point_addr =
 	    uif->altsetting[0].endpoint[isoc_pipe].desc.
 			bEndpointAddress;
@@ -714,8 +719,14 @@ static int cx231xx_audio_init(struct cx2
 	}
 
 	for (i = 0; i < adev->num_alt; i++) {
-		u16 tmp =
-		    le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].desc.
+		u16 tmp;
+
+		if (uif->altsetting[i].desc.bNumEndpoints < isoc_pipe + 1) {
+			err = -ENODEV;
+			goto err_free_pkt_size;
+		}
+
+		tmp = le16_to_cpu(uif->altsetting[i].endpoint[isoc_pipe].desc.
 				wMaxPacketSize);
 		adev->alt_max_pkt_size[i] =
 		    (tmp & 0x07ff) * (((tmp & 0x1800) >> 11) + 1);
@@ -725,6 +736,8 @@ static int cx231xx_audio_init(struct cx2
 
 	return 0;
 
+err_free_pkt_size:
+	kfree(adev->alt_max_pkt_size);
 err_free_card:
 	snd_card_free(card);