From: Kurt Kanzenbach <kurt@linutronix.de>
To: Colin King <colin.king@canonical.com>,
Andrew Lunn <andrew@lunn.ch>,
Vivien Didelot <vivien.didelot@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>,
Vladimir Oltean <olteanv@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] net: dsa: fix unintended sign extension on a u16 left shift
Date: Mon, 09 Nov 2020 13:27:52 +0000 [thread overview]
Message-ID: <87y2jar76v.fsf@kurt> (raw)
In-Reply-To: <20201109124008.2079873-1-colin.king@canonical.com>
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On Mon Nov 09 2020, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> The left shift of u16 variable high is promoted to the type int and
> then sign extended to a 64 bit u64 value. If the top bit of high is
> set then the upper 32 bits of the result end up being set by the
> sign extension. Fix this by explicitly casting the value in high to
> a u64 before left shifting by 16 places.
>
> Also, remove the initialisation of variable value to 0 at the start
> of each loop iteration as the value is never read and hence the
> assignment it is redundant.
>
> Addresses-Coverity: ("Unintended sign extension")
> Fixes: e4b27ebc780f ("net: dsa: Add DSA driver for Hirschmann Hellcreek switches")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
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WARNING: multiple messages have this Message-ID (diff)
From: Kurt Kanzenbach <kurt@linutronix.de>
To: Colin King <colin.king@canonical.com>,
Andrew Lunn <andrew@lunn.ch>,
Vivien Didelot <vivien.didelot@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>,
Vladimir Oltean <olteanv@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] net: dsa: fix unintended sign extension on a u16 left shift
Date: Mon, 09 Nov 2020 14:27:52 +0100 [thread overview]
Message-ID: <87y2jar76v.fsf@kurt> (raw)
In-Reply-To: <20201109124008.2079873-1-colin.king@canonical.com>
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On Mon Nov 09 2020, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> The left shift of u16 variable high is promoted to the type int and
> then sign extended to a 64 bit u64 value. If the top bit of high is
> set then the upper 32 bits of the result end up being set by the
> sign extension. Fix this by explicitly casting the value in high to
> a u64 before left shifting by 16 places.
>
> Also, remove the initialisation of variable value to 0 at the start
> of each loop iteration as the value is never read and hence the
> assignment it is redundant.
>
> Addresses-Coverity: ("Unintended sign extension")
> Fixes: e4b27ebc780f ("net: dsa: Add DSA driver for Hirschmann Hellcreek switches")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Kurt Kanzenbach <kurt@linutronix.de>
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next prev parent reply other threads:[~2020-11-09 13:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-09 12:40 [PATCH][next] net: dsa: fix unintended sign extension on a u16 left shift Colin King
2020-11-09 12:40 ` Colin King
2020-11-09 12:51 ` Kurt Kanzenbach
2020-11-09 12:51 ` Kurt Kanzenbach
2020-11-09 13:27 ` Kurt Kanzenbach [this message]
2020-11-09 13:27 ` Kurt Kanzenbach
2020-11-11 1:48 ` Jakub Kicinski
2020-11-11 1:48 ` Jakub Kicinski
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