[ 3.8.y.z extended stable ] Patch "HID: multitouch: validate indexes details" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    HID: multitouch: validate indexes details

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.11.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 0946700f31b91871b837b3e2c39e37c2dde66d53 Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <benjamin.tissoires at redhat.com>
Date: Wed, 11 Sep 2013 21:56:58 +0200
Subject: HID: multitouch: validate indexes details

commit 8821f5dc187bdf16cfb32ef5aa8c3035273fa79a upstream.

When working on report indexes, always validate that they are in bounds.
Without this, a HID device could report a malicious feature report that
could trick the driver into a heap overflow:

[  634.885003] usb 1-1: New USB device found, idVendor=0596, idProduct=0500
...
[  676.469629] BUG kmalloc-192 (Tainted: G        W   ): Redzone overwritten

Note that we need to change the indexes from s8 to s16 as they can
be between -1 and 255.

CVE-2013-2897

Signed-off-by: Benjamin Tissoires <benjamin.tissoires at redhat.com>
Acked-by: Kees Cook <keescook at chromium.org>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
[ kamal: backport to 3.8 (context) ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/hid/hid-multitouch.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 61543c0..071c288 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -85,9 +85,9 @@ struct mt_device {
 					   multitouch fields */
 	unsigned last_field_index;	/* last field index of the report */
 	unsigned last_slot_field;	/* the last field of a slot */
-	__s8 inputmode;		/* InputMode HID feature, -1 if non-existent */
-	__s8 inputmode_index;	/* InputMode HID feature index in the report */
-	__s8 maxcontact_report_id;	/* Maximum Contact Number HID feature,
+	__s16 inputmode;	/* InputMode HID feature, -1 if non-existent */
+	__s16 inputmode_index;	/* InputMode HID feature index in the report */
+	__s16 maxcontact_report_id;	/* Maximum Contact Number HID feature,
 				   -1 if non-existent */
 	__u8 num_received;	/* how many contacts we received */
 	__u8 num_expected;	/* expected last contact index */
@@ -268,20 +268,18 @@ static void mt_feature_mapping(struct hid_device *hdev,
 		struct hid_field *field, struct hid_usage *usage)
 {
 	struct mt_device *td = hid_get_drvdata(hdev);
-	int i;

 	switch (usage->hid) {
 	case HID_DG_INPUTMODE:
-		td->inputmode = field->report->id;
-		td->inputmode_index = 0; /* has to be updated below */
-
-		for (i=0; i < field->maxusage; i++) {
-			if (field->usage[i].hid == usage->hid) {
-				td->inputmode_index = i;
-				break;
-			}
+		/* Ignore if value index is out of bounds. */
+		if (usage->usage_index >= field->report_count) {
+			dev_err(&hdev->dev, "HID_DG_INPUTMODE out of range\n");
+			break;
 		}

+		td->inputmode = field->report->id;
+		td->inputmode_index = usage->usage_index;
+
 		break;
 	case HID_DG_CONTACTMAX:
 		td->maxcontact_report_id = field->report->id;
@@ -459,6 +457,10 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTCOUNT:
+			/* Ignore if indexes are out of bounds. */
+			if (field->index >= field->report->maxfield ||
+			    usage->usage_index >= field->report_count)
+				return 1;
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTMAX:
--
1.8.1.2