linux-kernel - Re: [PATCH] atm: he: fix sign-extension overflow on large shift

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Message-Id: <20190117.114753.495905826813982221.davem@davemloft.net>
Date:   Thu, 17 Jan 2019 11:47:53 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     colin.king@...onical.com
Cc:     3chas3@...il.com, linux-atm-general@...ts.sourceforge.net,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] atm: he: fix sign-extension overflow on large shift

From: Colin King <colin.king@...onical.com>
Date: Tue, 15 Jan 2019 18:03:38 +0000

> From: Colin Ian King <colin.king@...onical.com>
> 
> Shifting the 1 by exp by an int can lead to sign-extension overlow when
> exp is 31 since 1 is an signed int and sign-extending this result to an
> unsigned long long will set the upper 32 bits.  Fix this by shifting an
> unsigned long.
> 
> Detected by cppcheck:
> (warning) Shifting signed 32-bit value by 31 bits is undefined behaviour
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Applied.