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 9BCFF6A32A; Tue, 5 Dec 2023 17:53:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bOHvhhhG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 99653C433C8; Tue, 5 Dec 2023 17:53:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701798785; bh=qND1Cy64uVoi7dcRD4f9PhuWzWNexF0SFLJhlxPZ91E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bOHvhhhGxvy2Z/wb90CKjL692W3BqYaNIrPBlQ8ImdyJIOGtjD2j7xMkgGxaMhwXY kuQgjFkYAtPqKyCh+i4sbbU9AG9ZdJez5q9PL41RjRm1ErlRBqIYPEu6k0e02lLhM+ aunfDl2k5E/MtUGpqtUdJ1blRg4NVZX8tdW5gqyY2FLk6MBHa/bQHiqK4ioRuGExQL /Ce9YdeDBNPfVf6BNBOuVMw5uaTnSM2pZMmwaXZi59+56lmcGv28gkYmhoYoBqZsRB 3R7j/RRT3DyigF/LuAdEK4Nj7d+x5uL4nQSQ8uj1XzadQYLqbBZIhIYzLZSN5kWL0q T1OMbB5r4kInw== Date: Tue, 5 Dec 2023 10:53:02 -0700 From: Nathan Chancellor To: richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net Cc: ndesaulniers@google.com, trix@redhat.com, linux-um@lists.infradead.org, llvm@lists.linux.dev, patches@lists.linux.dev, kernel test robot Subject: Re: [PATCH] um: net: Fix return type of uml_net_start_xmit() Message-ID: <20231205175302.GA536347@dev-arch.thelio-3990X> References: <20231003-um-net-wifpts-v1-1-02888c634ee7@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231003-um-net-wifpts-v1-1-02888c634ee7@kernel.org> Ping? I would like to turn this warning on for W=1 and the kbuild test robot flagged this instance. If the UML folks don't want to carry it, could I get an ack so that it could go with the warning enablement in the kbuild tree? https://lore.kernel.org/20231002-enable-wincompatible-function-pointer-types-strict-w-1-v1-1-808ab955d42d@kernel.org/ On Tue, Oct 03, 2023 at 11:35:53AM -0700, Nathan Chancellor wrote: > 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 > warning in clang aims to catch these at compile time, which reveals: > > arch/um/drivers/net_kern.c:353:21: warning: 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 *)' [-Wincompatible-function-pointer-types-strict] > 353 | .ndo_start_xmit = uml_net_start_xmit, > | ^~~~~~~~~~~~~~~~~~ > 1 warning generated. > > ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of > 'netdev_tx_t', not 'int'. Adjust the return type of uml_net_start_xmit() > to match the prototype's to resolve the warning. While UML does not > currently implement support for kCFI, it could in the future, which > means this warning becomes a fatal CFI failure at run time. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-kbuild-all/202310031340.v1vPh207-lkp@intel.com/ > Signed-off-by: Nathan Chancellor > --- > arch/um/drivers/net_kern.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c > index 3d7836c46507..cabcc501b448 100644 > --- a/arch/um/drivers/net_kern.c > +++ b/arch/um/drivers/net_kern.c > @@ -204,7 +204,7 @@ static int uml_net_close(struct net_device *dev) > return 0; > } > > -static int uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev) > +static netdev_tx_t uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev) > { > struct uml_net_private *lp = netdev_priv(dev); > unsigned long flags; > > --- > base-commit: 8a749fd1a8720d4619c91c8b6e7528c0a355c0aa > change-id: 20231003-um-net-wifpts-14a7429c7524 > > Best regards, > -- > Nathan Chancellor >