From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 836483A1CF; Mon, 19 Feb 2024 17:03:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708362182; cv=none; b=ds9m2qBiQwK3QfyHhSFHQc3dWu2MtfkudnmmxIQUBAXq3z6aiLD5cJgO8cxBWHC2DkpezcuMgHbukHe6FGTmuzrU9Zj6ZUdZ4vZbdtD4r0U7snYWCJWu75f6P2RBPx6oia9Fqx4lef4pyChF3sVEuXz8jr5aSXM4qeQLkMHyhaw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708362182; c=relaxed/simple; bh=FDHavmdGhoIJckd4BTDH4LTUQrUq5xigNG4PkIe8dTM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EW4qgtkk6W2S2U8lM2N2P2m+36FBk/uwskRiR9WKD7FTFiq3wMQsfVyq7VeKyd8TzmJYYAhnbqWpvmwaWN9idhFGkJd2E7+t7ILAvKYfBEkw11o4KB/TyQmxqrbomxw6Ni3clGbVLuoDoojCW37eu1eiMnero+SONT649kXY8aI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6C281DA7; Mon, 19 Feb 2024 09:03:39 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.67.88]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 370C13F762; Mon, 19 Feb 2024 09:02:58 -0800 (PST) Date: Mon, 19 Feb 2024 17:02:55 +0000 From: Mark Rutland To: Kees Cook Cc: Andy Shevchenko , "Gustavo A . R . Silva" , linux-hardening@vger.kernel.org, Rasmus Villemoes , Marco Elver , Eric Biggers , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 1/3] overflow: Adjust check_*_overflow() kern-doc to reflect results Message-ID: References: <20240214194432.makes.837-kees@kernel.org> <20240214194605.602505-1-keescook@chromium.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240214194605.602505-1-keescook@chromium.org> On Wed, Feb 14, 2024 at 11:46:01AM -0800, Kees Cook wrote: > The check_*_overflow() helpers will return results with potentially > wrapped-around values. These values have always been checked by the > selftests, so avoid the confusing language in the kern-doc. The idea of > "safe for use" was relative to the expectation of whether or not the > caller wants a wrapped value -- the calculation itself will always follow > arithmetic wrapping rules. > > Reviewed-by: Gustavo A. R. Silva > Signed-off-by: Kees Cook > --- > Cc: Mark Rutland > Cc: linux-hardening@vger.kernel.org Acked-by: Mark Rutland Mark. > --- > include/linux/overflow.h | 21 +++++++++------------ > 1 file changed, 9 insertions(+), 12 deletions(-) > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 7b5cf4a5cd19..ad64d810c8aa 100644 > --- a/include/linux/overflow.h > +++ b/include/linux/overflow.h > @@ -57,11 +57,10 @@ static inline bool __must_check __must_check_overflow(bool overflow) > * @b: second addend > * @d: pointer to store sum > * > - * Returns 0 on success. > + * Returns true on wrap-around, false otherwise. > * > - * *@d holds the results of the attempted addition, but is not considered > - * "safe for use" on a non-zero return value, which indicates that the > - * sum has overflowed or been truncated. > + * *@d holds the results of the attempted addition, regardless of whether > + * wrap-around occurred. > */ > #define check_add_overflow(a, b, d) \ > __must_check_overflow(__builtin_add_overflow(a, b, d)) > @@ -72,11 +71,10 @@ static inline bool __must_check __must_check_overflow(bool overflow) > * @b: subtrahend; value to subtract from @a > * @d: pointer to store difference > * > - * Returns 0 on success. > + * Returns true on wrap-around, false otherwise. > * > - * *@d holds the results of the attempted subtraction, but is not considered > - * "safe for use" on a non-zero return value, which indicates that the > - * difference has underflowed or been truncated. > + * *@d holds the results of the attempted subtraction, regardless of whether > + * wrap-around occurred. > */ > #define check_sub_overflow(a, b, d) \ > __must_check_overflow(__builtin_sub_overflow(a, b, d)) > @@ -87,11 +85,10 @@ static inline bool __must_check __must_check_overflow(bool overflow) > * @b: second factor > * @d: pointer to store product > * > - * Returns 0 on success. > + * Returns true on wrap-around, false otherwise. > * > - * *@d holds the results of the attempted multiplication, but is not > - * considered "safe for use" on a non-zero return value, which indicates > - * that the product has overflowed or been truncated. > + * *@d holds the results of the attempted multiplication, regardless of whether > + * wrap-around occurred. > */ > #define check_mul_overflow(a, b, d) \ > __must_check_overflow(__builtin_mul_overflow(a, b, d)) > -- > 2.34.1 >