linux-kernel - [PATCH] iio: maxim_thermocouple: detect invalid storage size in read()

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Message-Id: <20161025155538.38037-1-arnd@arndb.de>
Date:   Tue, 25 Oct 2016 17:55:04 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Matt Ranostay <mranostay@...il.com>,
        sayli karnik <karniksayli1995@...il.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iio: maxim_thermocouple: detect invalid storage size in read()

As found by gcc -Wmaybe-uninitialized, having a storage_bytes value other
than 2 or 4 will result in undefined behavior:

drivers/iio/temperature/maxim_thermocouple.c: In function 'maxim_thermocouple_read':
drivers/iio/temperature/maxim_thermocouple.c:141:5: error: 'ret' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This probably cannot happen, but returning -EINVAL here is appropriate
and makes gcc happy and the code more robust.

Fixes: 231147ee77f3 ("iio: maxim_thermocouple: Align 16 bit big endian value of raw reads")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/iio/temperature/maxim_thermocouple.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/temperature/maxim_thermocouple.c b/drivers/iio/temperature/maxim_thermocouple.c
index 066161a4bccd..f962f31a5eb2 100644
--- a/drivers/iio/temperature/maxim_thermocouple.c
+++ b/drivers/iio/temperature/maxim_thermocouple.c
@@ -136,6 +136,8 @@ static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
 		ret = spi_read(data->spi, (void *)&buf32, storage_bytes);
 		*val = be32_to_cpu(buf32);
 		break;
+	default:
+		ret = -EINVAL;
 	}
 
 	if (ret)
-- 
2.9.0