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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Pan Bian <bianpan2016@163.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.4 009/162] Input: cyttsp4_core - fix use after free bug
Date:   Thu, 19 Dec 2019 19:31:57 +0100
Message-Id: <20191219183201.355167767@linuxfoundation.org>
In-Reply-To: <20191219183150.477687052@linuxfoundation.org>
References: <20191219183150.477687052@linuxfoundation.org>
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From: Pan Bian <bianpan2016@163.com>

[ Upstream commit 79aae6acbef16f720a7949f8fc6ac69816c79d62 ]

The device md->input is used after it is released. Setting the device
data to NULL is unnecessary as the device is never used again. Instead,
md->input should be assigned NULL to avoid accessing the freed memory
accidently. Besides, checking md->si against NULL is superfluous as it
points to a variable address, which cannot be NULL.

Signed-off-by: Pan Bian <bianpan2016@163.com>
Link: https://lore.kernel.org/r/1572936379-6423-1-git-send-email-bianpan2016@163.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/input/touchscreen/cyttsp4_core.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/input/touchscreen/cyttsp4_core.c b/drivers/input/touchscreen/cyttsp4_core.c
index 5ed31057430c6..6e904048d1cb7 100644
--- a/drivers/input/touchscreen/cyttsp4_core.c
+++ b/drivers/input/touchscreen/cyttsp4_core.c
@@ -1972,11 +1972,6 @@ static int cyttsp4_mt_probe(struct cyttsp4 *cd)
 
 	/* get sysinfo */
 	md->si = &cd->sysinfo;
-	if (!md->si) {
-		dev_err(dev, "%s: Fail get sysinfo pointer from core p=%p\n",
-			__func__, md->si);
-		goto error_get_sysinfo;
-	}
 
 	rc = cyttsp4_setup_input_device(cd);
 	if (rc)
@@ -1986,8 +1981,6 @@ static int cyttsp4_mt_probe(struct cyttsp4 *cd)
 
 error_init_input:
 	input_free_device(md->input);
-error_get_sysinfo:
-	input_set_drvdata(md->input, NULL);
 error_alloc_failed:
 	dev_err(dev, "%s failed.\n", __func__);
 	return rc;
-- 
2.20.1