linux-kernel - Re: [PATCH 41/82] wil6210: Refactor intentional wrap-around test

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Message-ID: <87fryoeeuj.fsf@kernel.org>
Date: Tue, 23 Jan 2024 08:36:04 +0200
From: Kalle Valo <kvalo@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: linux-hardening@...r.kernel.org,  Johannes Berg
 <johannes.berg@...el.com>,  Max Chen <mxchen@...eaurora.org>,  Yang Shen
 <shenyang39@...wei.com>,  linux-wireless@...r.kernel.org,  "Gustavo A. R.
 Silva" <gustavoars@...nel.org>,  Bill Wendling <morbo@...gle.com>,  Justin
 Stitt <justinstitt@...gle.com>,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH 41/82] wil6210: Refactor intentional wrap-around test

Kees Cook <keescook@...omium.org> writes:

> In an effort to separate intentional arithmetic wrap-around from
> unexpected wrap-around, we need to refactor places that depend on this
> kind of math. One of the most common code patterns of this is:
>
> 	VAR + value < VAR
>
> Notably, this is considered "undefined behavior" for signed and pointer
> types, which the kernel works around by using the -fno-strict-overflow
> option in the build[1] (which used to just be -fwrapv). Regardless, we
> want to get the kernel source to the position where we can meaningfully
> instrument arithmetic wrap-around conditions and catch them when they
> are unexpected, regardless of whether they are signed[2], unsigned[3],
> or pointer[4] types.
>
> Refactor open-coded wrap-around addition test to use add_would_overflow().
> This paves the way to enabling the wrap-around sanitizers in the future.
>
> Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1]
> Link: https://github.com/KSPP/linux/issues/26 [2]
> Link: https://github.com/KSPP/linux/issues/27 [3]
> Link: https://github.com/KSPP/linux/issues/344 [4]
> Cc: Kalle Valo <kvalo@...nel.org>
> Cc: Johannes Berg <johannes.berg@...el.com>
> Cc: Max Chen <mxchen@...eaurora.org>
> Cc: Yang Shen <shenyang39@...wei.com>
> Cc: linux-wireless@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

I assume this goes via some other tree than wireless-next so:

Acked-by: Kalle Valo <kvalo@...nel.org>

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