netdev - Re: [PATCH] USB: hso: Fix OOB memory access in hso_probe/hso_get_config_data,Re: [PATCH] USB: hso: Fix OOB memory access in hso_probe/hso_get_config_data,Re: [PATCH] USB: hso: Fix OOB memory access in hso_probe/hso_get_config_data,Re: [PATCH] USB: hso: Fix OOB memory access in hso_probe/hso_get_config

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Date:   Sun, 9 Dec 2018 21:59:14 +0100
From:   Mathias Payer <mathias.payer@...elwelt.net>
To:     David Miller <davem@...emloft.net>
Cc:     gregkh@...uxfoundation.org, netdev@...r.kernel.org,
        linux-usb@...r.kernel.org, bigeasy@...utronix.de,
        benquike@...il.com
Subject: Re: [PATCH] USB: hso: Fix OOB memory access in
 hso_probe/hso_get_config_data,Re: [PATCH] USB: hso: Fix OOB memory access in
 hso_probe/hso_get_config_data,Re: [PATCH] USB: hso: Fix OOB memory access in
 hso_probe/hso_get_config_data,Re: [PATCH] USB: hso: Fix OOB memory access in
 hso_probe/hso_get_config_data



On 12/9/18 9:40 PM, David Miller wrote:
> From: Mathias Payer <mathias.payer@...elwelt.net>
> Date: Sun, 9 Dec 2018 21:17:58 +0100
> 
>> I've attached the updated patch. (Greg, please add your Signed-off-by).
> 
> Patches should be posted inline, not as attachments as per
> process/submitting-patches.rst

Sorry! And thanks for your patience, we're going through a learning experience.
Inlined updated patch with the discussed changes:

commit 78e4a03cd3ae7c8f5957a170bc054fd89d7600f1
Author: Mathias Payer <mathias.payer@...elwelt.net>
Date:   Sun Dec 9 16:45:09 2018 +0100

    NET: hso: Fix OOB memory access in hso_probe/hso_get_config_data in hso.c

    From: Hui Peng <benquike@...il.com>

    The function hso_probe reads if_num from the USB device (as an u8) and uses
    it without a length check to index an array, resulting in an OOB memory read
    in hso_probe or hso_get_config_data. Added a length check for both locations
    and updated hso_probe to bail on error.

    This issue has been assigned CVE-2018-19985.

    Reported-by: Hui Peng <benquike@...il.com>
    Reported-by: Mathias Payer <mathias.payer@...elwelt.net>
    Signed-off-by: Hui Peng <benquike@...il.com>
    Signed-off-by: Mathias Payer <mathias.payer@...elwelt.net>

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 184c24baca15..d6916f787fce 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2807,6 +2807,12 @@ static int hso_get_config_data(struct usb_interface
*interface)
 		return -EIO;
 	}

+	/* check if we have a valid interface */
+	if (if_num > 16) {
+		kfree(config_data);
+		return -EINVAL;
+	}
+
 	switch (config_data[if_num]) {
 	case 0x0:
 		result = 0;
@@ -2877,10 +2883,18 @@ static int hso_probe(struct usb_interface *interface,

 	/* Get the interface/port specification from either driver_info or from
 	 * the device itself */
-	if (id->driver_info)
+	if (id->driver_info) {
+		/* if_num is controlled by the device, driver_info is a 0 terminated
+		 * array. Make sure, the access is in bounds! */
+		for (i = 0; i <= if_num; ++i)
+			if (((u32 *)(id->driver_info))[i] == 0)
+				goto exit;
 		port_spec = ((u32 *)(id->driver_info))[if_num];
-	else
+	} else {
 		port_spec = hso_get_config_data(interface);
+		if (port_spec < 0)
+			goto exit;
+	}

 	/* Check if we need to switch to alt interfaces prior to port
 	 * configuration */



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