linux-hardening - Re: [PATCH][next] gve: Use size_add() in call to struct

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Message-ID: <202309151144.E420B9F8@keescook>
Date:   Fri, 15 Sep 2023 11:44:40 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Jeroen de Borst <jeroendb@...gle.com>,
        Praveen Kaligineedi <pkaligineedi@...gle.com>,
        Shailend Chand <shailend@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] gve: Use size_add() in call to struct_size()

On Fri, Sep 15, 2023 at 12:17:49PM -0600, Gustavo A. R. Silva wrote:
> If, for any reason, `tx_stats_num + rx_stats_num` wraps around, the
> protection that struct_size() adds against potential integer overflows
> is defeated. Fix this by hardening call to struct_size() with size_add().
> 
> Fixes: 691f4077d560 ("gve: Replace zero-length array with flexible-array member")
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks, yes, this will maintain SIZE_MAX saturation if it happens.

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

-- 
Kees Cook