linux-kernel - Re: [PATCH] rtc: 88pm860x: fix unintended sign extension

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Message-ID: <20190207205322.GK4719@piout.net>
Date:   Thu, 7 Feb 2019 21:53:22 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>, linux-rtc@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: 88pm860x: fix unintended sign extension

On 06/02/2019 09:50:53+0000, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Shifting a u8 by 24 will cause the value to be promoted to an integer. If
> the top bit of the u8 is set then the following conversion to an unsigned
> long will sign extend the value causing the upper 32 bits to be set in
> the result.
> 
> Fix this by casting the u8 value to an unsigned long before the shift.
> 
> Detected by CoverityScan, CID#144925-144928 ("Unintended sign extension")
> 
> Fixes: 008b30408c40 ("mfd: Add rtc support to 88pm860x")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/rtc/rtc-88pm860x.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
Applied, thanks.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com