linux-hardening - Re: [PATCH][next] cifs: Replace a couple of one-element arrays with flexible-array members

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Message-ID: <202210042006.9A12D208@keescook>
Date:   Tue, 4 Oct 2022 20:06:41 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@....nz>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        Shyam Prasad N <sprasad@...rosoft.com>,
        Tom Talpey <tom@...pey.com>, linux-cifs@...r.kernel.org,
        samba-technical@...ts.samba.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] cifs: Replace a couple of one-element arrays with
 flexible-array members

On Tue, Oct 04, 2022 at 08:51:39PM -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 arrays with flexible-array
> member in structs negotiate_req and extended_response, and refactor the
> rest of the code, accordingly.
> 
> Also, make use of the DECLARE_FLEX_ARRAY() helper to declare flexible
> array member EncryptionKey in union u. This new helper allows for
> flexible-array members in unions.
> 
> Change pointer notation to proper array notation in a call to memcpy()
> where flexible-array member DialectsArray is being used as destination
> argument.
> 
> Important to mention is that doing a build before/after this patch results
> in no binary output differences.
> 
> 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/229
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Looks good to me; thanks!

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

-- 
Kees Cook