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[2620:137:e000::1:20]) by mx.google.com with ESMTP id f6-20020a170902ce8600b00186ffe624e8si20810382plg.436.2022.11.02.09.40.14; Wed, 02 Nov 2022 09:40:39 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=k20201202 header.b=OVWh4pJE; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231803AbiKBQiV (ORCPT + 99 others); Wed, 2 Nov 2022 12:38:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231721AbiKBQh4 (ORCPT ); Wed, 2 Nov 2022 12:37:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F0C431DE1; Wed, 2 Nov 2022 09:33:01 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EDA8761A56; Wed, 2 Nov 2022 16:33:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C573C433C1; Wed, 2 Nov 2022 16:32:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667406780; bh=X6xqT5Q+gVJ0fSUPZGCRiXKotwL6OxS8B+0WmVkabE4=; h=From:To:Cc:Subject:Date:From; b=OVWh4pJER+b69tT/lzefyIZrWEZ5hg0SPIMfoJWLTsR9bJbMocFw4sqplf61P4ZTG o0V14tacLjtPAz4u8ic5H5OYNRr6xxm9P20i1jPDXC+ksocQi2J3QBCWd4sDxKgBg0 VSJdSVkI3PdRgsbebmf06LtHYSYZp5+9xrZZv9Jzyp3gl9erOAQeAWCQmZlSBsqREX /8nR88FXpSezKRBWnpTKSweTw9QSu8EbYBP2a8ECv/uS6eBr74jBY+kk0ttipIKWWH QJU/7XSrni5lMQ0YbkB2WKjJqEEBbkX+xnETcMD/8JXHgKGEXUt0OhU0rYuTyMPWy5 308C7CV67PCgA== From: Nathan Chancellor To: Alexandra Winter , Wenjia Zhang Cc: Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , linux-s390@vger.kernel.org, netdev@vger.kernel.org, Nick Desaulniers , Tom Rix , Kees Cook , Sami Tolvanen , llvm@lists.linux.dev, linux-kernel@vger.kernel.org, patches@lists.linux.dev, Nathan Chancellor Subject: [PATCH 1/3] s390/ctcm: Fix return type of ctc{mp,}m_tx() Date: Wed, 2 Nov 2022 09:32:50 -0700 Message-Id: <20221102163252.49175-1-nathan@kernel.org> X-Mailer: git-send-email 2.38.1 MIME-Version: 1.0 X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1748403214258154140?= X-GMAIL-MSGID: =?utf-8?q?1748403214258154140?= With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed. A proposed warning in clang aims to catch these at compile time, which reveals: drivers/s390/net/ctcm_main.c:1064:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict] .ndo_start_xmit = ctcm_tx, ^~~~~~~ drivers/s390/net/ctcm_main.c:1072:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict] .ndo_start_xmit = ctcmpc_tx, ^~~~~~~~~ ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of 'netdev_tx_t', not 'int'. Adjust the return type of ctc{mp,}m_tx() to match the prototype's to resolve the warning and potential CFI failure, should s390 select ARCH_SUPPORTS_CFI_CLANG in the future. Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Signed-off-by: Nathan Chancellor Reviewed-by: Kees Cook Reviewed-by: Alexandra Winter --- drivers/s390/net/ctcm_main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780 diff --git a/drivers/s390/net/ctcm_main.c b/drivers/s390/net/ctcm_main.c index 37b551bd43bf..4eea7d0285c1 100644 --- a/drivers/s390/net/ctcm_main.c +++ b/drivers/s390/net/ctcm_main.c @@ -834,7 +834,7 @@ static int ctcmpc_transmit_skb(struct channel *ch, struct sk_buff *skb) * the generic network layer. */ /* first merge version - leaving both functions separated */ -static int ctcm_tx(struct sk_buff *skb, struct net_device *dev) +static netdev_tx_t ctcm_tx(struct sk_buff *skb, struct net_device *dev) { struct ctcm_priv *priv = dev->ml_priv; @@ -877,7 +877,7 @@ static int ctcm_tx(struct sk_buff *skb, struct net_device *dev) } /* unmerged MPC variant of ctcm_tx */ -static int ctcmpc_tx(struct sk_buff *skb, struct net_device *dev) +static netdev_tx_t ctcmpc_tx(struct sk_buff *skb, struct net_device *dev) { int len = 0; struct ctcm_priv *priv = dev->ml_priv;