linux-kernel - Re: [PATCH v8 15/19] staging: r8188eu: change the type of a variable in rtw

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Date:   Mon, 20 Sep 2021 15:03:44 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Skripkin <paskripkin@...il.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        David Laight <david.Laight@...lab.com>,
        Martin Kaiser <martin@...ser.cx>
Subject: Re: [PATCH v8 15/19] staging: r8188eu: change the type of a variable in rtw_read16()

On Monday, September 20, 2021 1:56:47 PM CEST Dan Carpenter wrote:
> On Mon, Sep 20, 2021 at 01:53:52AM +0200, Fabio M. De Francesco wrote:
> > Change the type of "data" from __le32 to __le16.
> > 
> 
> You should note in the commit message that:
> 
> The last two bytes of "data" are not initialized so the le32_to_cpu(data)
> technically reads uninitialized data.  This can likely be detected by
> the KASan checker as reading uninitialized data.  But because the bytes
> are discarded in the end so this will not affect runtime.
> 
> regards,
> dan carpenter
> 

Dear Dan,

Thanks for your suggestion about this specific topic. 

We thought that, since "data" is in bitwise AND with 0xffff before being 
passed to the callee, it was enough to have reviewers know why we're doing 
that change of type with no further explanations. Actually it seems to be not 
enough to motivate that change.

We will surely use the note you provided. 

However, since I'm not used to blindly follow suggestions (even if I trust 
your words with no doubts at all) without complete understanding of what I'm 
doing, I will need to understand what KASan is before copy-paste your note.

Thank you very much,

Fabio