linux-kernel - [PATCH 4.19 263/425] mt7601u: fix always true expression

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Message-Id: <20210520092140.091838814@linuxfoundation.org>
Date:   Thu, 20 May 2021 11:20:32 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Colin Ian King <colin.king@...onical.com>,
        Jakub Kicinski <kubakici@...pl>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 263/425] mt7601u: fix always true expression

From: Colin Ian King <colin.king@...onical.com>

[ Upstream commit 87fce88658ba047ae62e83497d3f3c5dc22fa6f9 ]

Currently the expression ~nic_conf1 is always true because nic_conf1
is a u16 and according to 6.5.3.3 of the C standard the ~ operator
promotes the u16 to an integer before flipping all the bits. Thus
the top 16 bits of the integer result are all set so the expression
is always true.  If the intention was to flip all the bits of nic_conf1
then casting the integer result back to a u16 is a suitabel fix.

Interestingly static analyzers seem to thing a bitwise ! should be
used instead of ~ for this scenario, so I think the original intent
of the expression may need some extra consideration.

Addresses-Coverity: ("Logical vs. bitwise operator")
Fixes: c869f77d6abb ("add mt7601u driver")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
Acked-by: Jakub Kicinski <kubakici@...pl>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Link: https://lore.kernel.org/r/20210225183241.1002129-1-colin.king@canonical.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/mediatek/mt7601u/eeprom.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt7601u/eeprom.c b/drivers/net/wireless/mediatek/mt7601u/eeprom.c
index 76117b402880..6ab1035e4a12 100644
--- a/drivers/net/wireless/mediatek/mt7601u/eeprom.c
+++ b/drivers/net/wireless/mediatek/mt7601u/eeprom.c
@@ -107,7 +107,7 @@ mt7601u_has_tssi(struct mt7601u_dev *dev, u8 *eeprom)
 {
 	u16 nic_conf1 = get_unaligned_le16(eeprom + MT_EE_NIC_CONF_1);
 
-	return ~nic_conf1 && (nic_conf1 & MT_EE_NIC_CONF_1_TX_ALC_EN);
+	return (u16)~nic_conf1 && (nic_conf1 & MT_EE_NIC_CONF_1_TX_ALC_EN);
 }
 
 static void
-- 
2.30.2