[3.13.y-ckt stable] Patch "HID: i2c-hid: Limit reads to wMaxInputLength bytes for input events" 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: i2c-hid: Limit reads to wMaxInputLength bytes for input events

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt18.

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

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 684b91eb2a9fd0213d9d6fae326bf6ec4b459b14 Mon Sep 17 00:00:00 2001
From: Seth Forshee <seth.forshee at canonical.com>
Date: Fri, 20 Feb 2015 11:45:11 -0600
Subject: HID: i2c-hid: Limit reads to wMaxInputLength bytes for input events

commit 6d00f37e49d95e640a3937a4a1ae07dbe92a10cb upstream.

d1c7e29e8d27 (HID: i2c-hid: prevent buffer overflow in early IRQ)
changed hid_get_input() to read ihid->bufsize bytes, which can be
more than wMaxInputLength. This is the case with the Dell XPS 13
9343, and it is causing events to be missed. In some cases the
missed events are releases, which can cause the cursor to jump or
freeze, among other problems. Limit the number of bytes read to
min(wMaxInputLength, ihid->bufsize) to prevent such problems.

Fixes: d1c7e29e8d27 "HID: i2c-hid: prevent buffer overflow in early IRQ"
Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires at redhat.com>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/hid/i2c-hid/i2c-hid.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index 05c2134..cc4b092 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -356,7 +356,10 @@ static int i2c_hid_hwreset(struct i2c_client *client)
 static void i2c_hid_get_input(struct i2c_hid *ihid)
 {
 	int ret, ret_size;
-	int size = ihid->bufsize;
+	int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);
+
+	if (size > ihid->bufsize)
+		size = ihid->bufsize;

 	ret = i2c_master_recv(ihid->client, ihid->inbuf, size);
 	if (ret != size) {
--
1.9.1