From patchwork Tue Jan 23 00:27:07 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 13526720 Received: from mail-oo1-f44.google.com (mail-oo1-f44.google.com [209.85.161.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 31536612F1 for ; Tue, 23 Jan 2024 00:45:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.44 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705970757; cv=none; b=Wv5mwuI/YgmoeaghTHq+Y06JwGWotstT6lVkCGsTcaPCoRh6xTPFcjwDuKD4uvu8jyz5BBlYIC+Bw3Ljn45X3faKIoDotuSPM7Vt6LedslZBXkQYKPBTQLVct4FKl4+R5cKbiDMiuJGiM48JvgKxygt8XO9dcXJO3eNv7jVHTK8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705970757; c=relaxed/simple; bh=wEJz6ncP+qRtXKX7k2D+joSrafVF4O5OSdQFr3cojK4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=oLBLCXQDu/zxeKe11MnT+LmuI/1qiIHdDRr+z7KqwQ4n3V87KpZ2Y5m1HA48ZIVHiUlAONILUR99LpE9MxeWYDkScDailtBXmOxLiBlrzV2oNbwYTGETN03maGGL00AV2Xar0iXN27FTL3XLieGiQvf1p+QE4uqLtIy5OLfJ1hE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=G3Lo3qW7; arc=none smtp.client-ip=209.85.161.44 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="G3Lo3qW7" Received: by mail-oo1-f44.google.com with SMTP id 006d021491bc7-599a5266066so54703eaf.1 for ; Mon, 22 Jan 2024 16:45:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1705970755; x=1706575555; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=dOtaS8Q/PpRJgiodelWT3IFfX/962bDrzicKtXvnvo8=; b=G3Lo3qW7qs+sdo6ikHuS/j4yt/01dQGAj9Ib1ApRTJyVwP3IEiI4DgknpJ89s7oXCh aVFUzX2sLjVajlDTA9YmvkTVVJVylqhmBNcZV7VzqZKuSA4tWuWouW9/FkvqsoGjpREQ w6k9tubHuLfMzKDj5I3iOuYTQh5vxAE8WY+q0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1705970755; x=1706575555; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=dOtaS8Q/PpRJgiodelWT3IFfX/962bDrzicKtXvnvo8=; b=usw6yuwNv5z2OJWpVc/iKzoKlFshaQM6NNUBrSRSqA1ctmiAfERf6f1aoExJFbeZ9O +qFQxdxow4WlGHUgQsXaDmv1CxVpg9XBSL9IboU2RyVO4fgXTzQulqpG7cQD+UDwDfGu q7AxSSydusNnUntiztGGY7amD05UJICA0DYE2y8pzeIjO/OHXisTgPytUJcl5/MHiXse jAeNutPBofRrfExoNeBel8AwxxBjznYmJmowdERxNUbcgSjQZRat93pQ0os3yOiXvfPf yQl81o/pZ7kZvi5/Zv6lfv0DYtKtVzNa5wehR9yW4DcsJV2qKMXXNgAaBcdIKCQA2Drj K0xw== X-Gm-Message-State: AOJu0YzAf/qsUq98Rd6+09Ey/wgRHy367b4YElxA0NUxQZeO9IGYN/ay xg0xQw/ktai1ClMgnPBr6KWUjZGHayrHpzLBy0+kbmb+gL78W1zpQrDQBpjJwg== X-Google-Smtp-Source: AGHT+IGQwShADBm43GhljCU0u40cOaLZ1q4WsuoH3YKek1HoSlz9pHA07/Hox4IaetxxaQSRrpFeCQ== X-Received: by 2002:a05:6358:99a0:b0:176:3e0d:9910 with SMTP id j32-20020a05635899a000b001763e0d9910mr4500624rwb.0.1705970755199; Mon, 22 Jan 2024 16:45:55 -0800 (PST) Received: from www.outflux.net ([198.0.35.241]) by smtp.gmail.com with ESMTPSA id g4-20020aa78744000000b006d9bb4400f0sm10234582pfo.88.2024.01.22.16.45.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jan 2024 16:45:54 -0800 (PST) From: Kees Cook To: linux-hardening@vger.kernel.org Cc: Kees Cook , "Michael S. Tsirkin" , Jason Wang , kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, "Gustavo A. R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 32/82] vringh: Refactor intentional wrap-around calculation Date: Mon, 22 Jan 2024 16:27:07 -0800 Message-Id: <20240123002814.1396804-32-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2682; i=keescook@chromium.org; h=from:subject; bh=wEJz6ncP+qRtXKX7k2D+joSrafVF4O5OSdQFr3cojK4=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgHD0u3YhpYy/8Dc5chh0+01JehokeF1vpzI BT65uKVfgWJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8IBwAKCRCJcvTf3G3A JpFyEACdChSCT4Y0X47ea6T+PsrgS42Vou9eXn9FDMWCPIbD1kW1gHAFP1FAqkYnEij+0625LYZ 2RtZVv0zZFrtRaGdtFZFQFDJTSr6QNj3uxivVtsmwb1pLXXDnFTFWikADuH5v60qkgSrb2bTZMY knyNpBo6L+ItzkaxgMhFX1rtdBM2iTj2HOYKmNkYIwvxCNExT4h+7TKnDNipWpdd5EwB3nV3F2p 1pExl5eEqmY2Ma6oIf7cypf/bIKRIjUW1Ilre5bbCngLzeYZMqOG35bUlr3WC3w88nu6tYBXolx Erl0eGsiamN+wyuoxNKoT/h+WyXer3JpoxEq/sl38I39B23XaYVff/d+6Suvc+F3tV6jNdbyaem JxwjjNG4ksbLc5PdSetTuaRGyP3xwIiVRJmS3tlng0ghnRbKVS/FFw+qU64g1HMXFJ/qj6Ldypv ORamulyXPJU2FWA/g8/Ld+OnSQn41XCT6619haypc24tpwo9TMSlKhckwkeIgqTxMWBfiha0co8 ANuXzPXBosDOYCZNhGhwsT9JNpMKS9otU4fcb4uoJ2RtASuAmGm82JgroIBM/MhrLeYmlZOwIk4 jIzar8S+YFZz03aIUIiOxVH9cIhd+DZLz1UZb5Pc9SBnZc4u8HlyhSQOPf8eOZtvyR3Q+n8534w TxS3x9dEXm4+h9g== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 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 unsigned wrap-around addition test to use check_add_overflow(), retaining the result for later usage (which removes the redundant open-coded addition). This paves the way to enabling the unsigned wrap-around sanitizer[2] 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: "Michael S. Tsirkin" Cc: Jason Wang Cc: kvm@vger.kernel.org Cc: virtualization@lists.linux.dev Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook Acked-by: Eugenio Pérez --- drivers/vhost/vringh.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 7b8fd977f71c..07442f0a52bd 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -145,6 +145,8 @@ static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len, bool (*getrange)(struct vringh *, u64, struct vringh_range *)) { + u64 sum; + if (addr < range->start || addr > range->end_incl) { if (!getrange(vrh, addr, range)) return false; @@ -152,20 +154,20 @@ static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len, BUG_ON(addr < range->start || addr > range->end_incl); /* To end of memory? */ - if (unlikely(addr + *len == 0)) { + if (unlikely(U64_MAX - addr == *len)) { if (range->end_incl == -1ULL) return true; goto truncate; } /* Otherwise, don't wrap. */ - if (addr + *len < addr) { + if (check_add_overflow(addr, *len, &sum)) { vringh_bad("Wrapping descriptor %zu@0x%llx", *len, (unsigned long long)addr); return false; } - if (unlikely(addr + *len - 1 > range->end_incl)) + if (unlikely(sum - 1 > range->end_incl)) goto truncate; return true;