linux-kernel - Re: [PATCH] scsi: pm8001: Replace one-element array with flexible-array member

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Message-ID: <202209232203.2F77ADD1CA@keescook>
Date:   Fri, 23 Sep 2022 22:21:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Jack Wang <jinpu.wang@...ud.ionos.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] scsi: pm8001: Replace one-element array with
 flexible-array member

On Thu, Sep 22, 2022 at 02:30:28PM -0500, Gustavo A. R. Silva wrote:
> One-element arrays are deprecated, and we are replacing them with flexible
> array members instead. So, replace one-element array with flexible-array
> member in struct fw_control_info.

I think this changelog should include some explanation of why this change
is safe. As far as I can see, it would be:

This is the only change needed; struct fw_control_info is only ever used
for casting to existing allocations. No sizeof() is used on any of the
resulting variables.

> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/207
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Another one down! :)

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook