linux-kernel - Re: [PATCH][next] wifi: mac80211: Add __counted_by for struct ieee802_11_elems and use struct

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Message-ID: <202310091257.6613605D5@keescook>
Date:   Mon, 9 Oct 2023 12:57:49 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Johannes Berg <johannes@...solutions.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] wifi: mac80211: Add __counted_by for struct
 ieee802_11_elems and use struct_size()

On Mon, Oct 09, 2023 at 11:59:41AM -0600, Gustavo A. R. Silva wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
> array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> While there, use struct_size() helper, instead of the open-coded
> version, to calculate the size for the allocation of the whole
> flexible structure including, of course, the flexible-array member.
> 
> This code was found with the help of Coccinelle, and audited and
> fixed manually.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Looks correct: "scratch" isn't accessed before setting "scratch_len".

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

-Kees

-- 
Kees Cook