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 C533A1E9F9; Wed, 2 Nov 2022 16:33:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ADFACC433D6; Wed, 2 Nov 2022 16:33:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667406789; bh=ZaNRk9XsK/SEJ/1Ji5JmKKMuERlYmmNZ5RDlsKv/yN8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YkVMEabLh2tHVOFpCHakFtCLP59LlHSUfhdMWu4i1Q1oy/ymN30vFMERBTMkgdtTp ymq2lbFxZGBSxqGhAKdJ2eIb4EQmAYcd2YP66adzMbb7iCa7xd3wZjEnRTetrxt732 1gxaC0PL4fvKZG0KVkxYTKo37/SVTYmmtxQG7DgvSBddVORZ/ccgUDj+RlitrmfmAo Yly3QDywW6xb+a1xY8w3fAhNkO4EwxTL/FQRrz0rQ6Cc0Z0ZP3fpn926O/J6pn/hl3 n8M/jPLP8WOu/JqkrFOqqhX49MQiUi7MZHrGzLzVb74m6Uo+LNodiPWEj0a3ZitXaH 0MvTDIz3zA8rA== 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 3/3] s390/lcs: Fix return type of lcs_start_xmit() Date: Wed, 2 Nov 2022 09:32:52 -0700 Message-Id: <20221102163252.49175-3-nathan@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221102163252.49175-1-nathan@kernel.org> References: <20221102163252.49175-1-nathan@kernel.org> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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/lcs.c:2090:21: 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 = lcs_start_xmit, ^~~~~~~~~~~~~~ drivers/s390/net/lcs.c:2097:21: 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 = lcs_start_xmit, ^~~~~~~~~~~~~~ ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of 'netdev_tx_t', not 'int'. Adjust the return type of lcs_start_xmit() 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 --- drivers/s390/net/lcs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c index 84c8981317b4..4cbb9802bf22 100644 --- a/drivers/s390/net/lcs.c +++ b/drivers/s390/net/lcs.c @@ -1519,7 +1519,7 @@ lcs_txbuffer_cb(struct lcs_channel *channel, struct lcs_buffer *buffer) /* * Packet transmit function called by network stack */ -static int +static netdev_tx_t __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb, struct net_device *dev) { @@ -1582,7 +1582,7 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb, return rc; } -static int +static netdev_tx_t lcs_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct lcs_card *card; -- 2.38.1