linux-kernel - Re: pwm: Fix double shift bug

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Message-ID: <2024060807-monument-unlocked-781b@gregkh>
Date: Sat, 8 Jun 2024 13:37:45 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: "Ivan T. Ivanov" <iivanov@...e.de>
Cc: cve@...nel.org, linux-cve-announce@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: pwm: Fix double shift bug

On Wed, Jun 05, 2024 at 05:43:05PM +0300, Ivan T. Ivanov wrote:
> Hi,
> 
> I could argue that this is not CVE at all. It changes just bit positions.
> 
> -	PWMF_REQUESTED = 1 << 0,
> -	PWMF_EXPORTED = 1 << 1,
> +	PWMF_REQUESTED = 0,
> +	PWMF_EXPORTED = 1,
> 
> ie. before fix they 1 and 2 and after the fix 0, 1.
> 
> All call sites are using set/test_bit() on unsigned long flags.
> 
> Yes, double shift do not look right, but I don't see how
> this could lead to malfunction, let alone a CVE.

It could be an issue if the values were larger than 5 as the commit
says, but that's not the case here, so you are correct and this has now
been rejected as a cve.

Thanks for the review!

greg k-h