From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3EBDF303C9B; Tue, 30 Sep 2025 14:56:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244193; cv=none; b=Hv5+0tUE/0EglXg35QcWu3XTNCG67Gq0zLdIh5GCJeJEFm5gKZCzsZgTkFgeEJVipa4iNGQhO3rIwqzDPdvgbywvE6gR4hilCf/tHWArqAaKVIYtdX35Ql5LEiDzXJ/upk+q68yhOLMXKZuAA6zPM9HYjYutmwr6Efuc5JLGrsY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759244193; c=relaxed/simple; bh=s1lYkbb+4CyWmvQY8AvrB88kdw5TrnIzjIYKm0N4Tlg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KdckguwWFjeyCI+ZQ1oxBmdLHpS89xbprdeTbx04l1EIPFKKnO442c6FaHpZ7lHMj8QKEIvSOeG/Ad6IN6QZqJKbv+edW0S3Ngpv3jZyn09F21DgFPbhp9B76ugnS3IWtf0sGK9XKzJV2Q/p2gUoeosW7gSMBscQQTj25t8uBxk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FRp74jbw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FRp74jbw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC7E0C113D0; Tue, 30 Sep 2025 14:56:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1759244193; bh=s1lYkbb+4CyWmvQY8AvrB88kdw5TrnIzjIYKm0N4Tlg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FRp74jbwkfpajSXk9hwd0qLDn7agwdg+CmbLtbLbR1cOWZnHK2CPViw4yBgEAOTiz CAcijJHDtQPlb5RHpNL1GpM9RPX4cnPeGtL4rVV94mctn6FUktQ03oVvX3hL2nUtIe 8o46zzE51jTDuVsz61NzzLoIpfCJYu6pc6ggLvt8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Rasmus Villemoes , Gwan-gyeong Mun , "Gustavo A. R. Silva" , Nick Desaulniers , linux-hardening@vger.kernel.org, Andrzej Hajda , Kees Cook , Eliav Farber Subject: [PATCH 5.10 014/122] overflow: Allow mixed type arguments Date: Tue, 30 Sep 2025 16:45:45 +0200 Message-ID: <20250930143823.574238011@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250930143822.939301999@linuxfoundation.org> References: <20250930143822.939301999@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kees Cook commit d219d2a9a92e39aa92799efe8f2aa21259b6dd82 upstream. When the check_[op]_overflow() helpers were introduced, all arguments were required to be the same type to make the fallback macros simpler. However, now that the fallback macros have been removed[1], it is fine to allow mixed types, which makes using the helpers much more useful, as they can be used to test for type-based overflows (e.g. adding two large ints but storing into a u8), as would be handy in the drm core[2]. Remove the restriction, and add additional self-tests that exercise some of the mixed-type overflow cases, and double-check for accidental macro side-effects. [1] https://git.kernel.org/linus/4eb6bd55cfb22ffc20652732340c4962f3ac9a91 [2] https://lore.kernel.org/lkml/20220824084514.2261614-2-gwan-gyeong.mun@intel.com Cc: Rasmus Villemoes Cc: Gwan-gyeong Mun Cc: "Gustavo A. R. Silva" Cc: Nick Desaulniers Cc: linux-hardening@vger.kernel.org Reviewed-by: Andrzej Hajda Reviewed-by: Gwan-gyeong Mun Tested-by: Gwan-gyeong Mun Signed-off-by: Kees Cook [ dropped the test portion of the commit as that doesn't apply to 5.15.y - gregkh] Signed-off-by: Greg Kroah-Hartman Signed-off-by: Eliav Farber Signed-off-by: Greg Kroah-Hartman --- include/linux/overflow.h | 72 ++++++++++++++++++++++++++--------------------- 1 file changed, 41 insertions(+), 31 deletions(-) --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -51,40 +51,50 @@ static inline bool __must_check __must_c return unlikely(overflow); } -/* - * For simplicity and code hygiene, the fallback code below insists on - * a, b and *d having the same type (similar to the min() and max() - * macros), whereas gcc's type-generic overflow checkers accept - * different types. Hence we don't just make check_add_overflow an - * alias for __builtin_add_overflow, but add type checks similar to - * below. +/** check_add_overflow() - Calculate addition with overflow checking + * + * @a: first addend + * @b: second addend + * @d: pointer to store sum + * + * Returns 0 on success. + * + * *@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. */ -#define check_add_overflow(a, b, d) __must_check_overflow(({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_add_overflow(__a, __b, __d); \ -})) +#define check_add_overflow(a, b, d) \ + __must_check_overflow(__builtin_add_overflow(a, b, d)) -#define check_sub_overflow(a, b, d) __must_check_overflow(({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_sub_overflow(__a, __b, __d); \ -})) +/** check_sub_overflow() - Calculate subtraction with overflow checking + * + * @a: minuend; value to subtract from + * @b: subtrahend; value to subtract from @a + * @d: pointer to store difference + * + * Returns 0 on success. + * + * *@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. + */ +#define check_sub_overflow(a, b, d) \ + __must_check_overflow(__builtin_sub_overflow(a, b, d)) -#define check_mul_overflow(a, b, d) __must_check_overflow(({ \ - typeof(a) __a = (a); \ - typeof(b) __b = (b); \ - typeof(d) __d = (d); \ - (void) (&__a == &__b); \ - (void) (&__a == __d); \ - __builtin_mul_overflow(__a, __b, __d); \ -})) +/** check_mul_overflow() - Calculate multiplication with overflow checking + * + * @a: first factor + * @b: second factor + * @d: pointer to store product + * + * Returns 0 on success. + * + * *@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. + */ +#define check_mul_overflow(a, b, d) \ + __must_check_overflow(__builtin_mul_overflow(a, b, d)) /** check_shl_overflow() - Calculate a left-shifted value and check overflow *