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From:   Michael Zaidman <michael.zaidman@gmail.com>
To:     jikos@kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-input@vger.kernel.org,
        linux-i2c@vger.kernel.org, Enrik.Berkhan@inka.de,
        Michael Zaidman <michael.zaidman@gmail.com>
Subject: [PATCH v4 11/13] HID: ft260: fix a NULL pointer dereference in ft260_i2c_write
Date:   Sat,  5 Nov 2022 23:11:49 +0200
Message-Id: <20221105211151.7094-12-michael.zaidman@gmail.com>
In-Reply-To: <20221105211151.7094-1-michael.zaidman@gmail.com>
References: <20221105211151.7094-1-michael.zaidman@gmail.com>
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The zero-length passed into the ft260_i2c_write() triggered the
NULL pointer dereference in the debug message on data[0] access.
Since the controller does not support a write of zero length,
let's not allow it.

Before:

$ sudo i2ctransfer -y 13 w0@0x51
Killed

After:

$ sudo i2ctransfer -y 13 w0@0x51
Error: Sending messages failed: Invalid argument

Reported-by: Enrik Berkhan <Enrik.Berkhan@inka.de>
Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
---
 drivers/hid/hid-ft260.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
index ac133980dfe9..b4f180c8750a 100644
--- a/drivers/hid/hid-ft260.c
+++ b/drivers/hid/hid-ft260.c
@@ -409,6 +409,9 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data,
 	struct ft260_i2c_write_request_report *rep =
 		(struct ft260_i2c_write_request_report *)dev->write_buf;
 
+	if (len < 1)
+		return -EINVAL;
+
 	rep->flag = FT260_FLAG_START;
 
 	do {
-- 
2.34.1