linux-hardening - Re: [PATCH][next] bnx2x: Replace one-element array with flexible-array member

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Message-ID: <20220204193827.019e7791@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Fri, 4 Feb 2022 19:38:27 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Ariel Elior <aelior@...vell.com>,
        Sudarsana Kalluru <skalluru@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] bnx2x: Replace one-element array with
 flexible-array member

On Fri, 4 Feb 2022 17:21:44 -0600 Gustavo A. R. Silva wrote:
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
> 
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
> 
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
> 
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.16/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Link: https://github.com/KSPP/linux/issues/79
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Would be useful to include the analysis confirming the change is safe
in this case, beyond the boiler plate commit message.

Reviewed-by: Jakub Kicinski <kuba@...nel.org>