linux-kernel - [PATCH 4.19 30/55] drivers/hid/hid-multitouch.c: fix a possible null pointer access.

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Message-Id: <20200130183614.135099635@linuxfoundation.org>
Date:   Thu, 30 Jan 2020 19:39:11 +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, Pan Zhang <zhangpan26@...wei.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 30/55] drivers/hid/hid-multitouch.c: fix a possible null pointer access.

From: Pan Zhang <zhangpan26@...wei.com>

[ Upstream commit 306d5acbfc66e7cccb4d8f91fc857206b8df80d1 ]

1002     if ((quirks & MT_QUIRK_IGNORE_DUPLICATES) && mt) {
1003         struct input_mt_slot *i_slot = &mt->slots[slotnum];
1004
1005         if (input_mt_is_active(i_slot) &&
1006             input_mt_is_used(mt, i_slot))
1007             return -EAGAIN;
1008     }

We previously assumed 'mt' could be null (see line 1002).

The following situation is similar, so add a judgement.

Signed-off-by: Pan Zhang <zhangpan26@...wei.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/hid/hid-multitouch.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 8403251992abb..19dfd8acd0dab 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1007,7 +1007,7 @@ static int mt_process_slot(struct mt_device *td, struct input_dev *input,
 		tool = MT_TOOL_DIAL;
 	else if (unlikely(!confidence_state)) {
 		tool = MT_TOOL_PALM;
-		if (!active &&
+		if (!active && mt &&
 		    input_mt_is_active(&mt->slots[slotnum])) {
 			/*
 			 * The non-confidence was reported for
-- 
2.20.1