From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86F0DC47092 for ; Mon, 24 May 2021 15:20:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 743F2613F4 for ; Mon, 24 May 2021 15:20:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235060AbhEXPUD (ORCPT ); Mon, 24 May 2021 11:20:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:40040 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234591AbhEXPIK (ORCPT ); Mon, 24 May 2021 11:08:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5816E61878; Mon, 24 May 2021 14:51:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621867895; bh=AkeUFwF6WPQBnzhsbWzH49A8ilmrlY6UJS1l6fLaMEc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Vr85qPTwnGROhQHOXOClQIo6KWcBfGBbkz4E1IhDqyC/Ve7GH4dh0KYVtO8biFzYY gnwh95OaQfqJW7aZFR2kRdmjnSPY+BfCKJrlCg4wqp40nO6Rbr4Q55G1uXhFjfnmdj /ei4iQD2VZFnMDFKG7bR6thmdKzXTYkTS9cUtAHlb6qz0IVeOitetnMYkxxWtLaRyX us0yyxc5ddsfT7y+w5UFfeDyCDB7QQe90WqXLnWtMqbPF48WZKvhtrbruRBxn4aquH 0IFRIZNNyQNAmAVYotmpITN87W+2h457jgmlSj4IpdsRPQuUtydpzWlV231DGBrdGE qTUhuKUfbmUgQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Du Cheng , "David S . Miller" , Greg Kroah-Hartman , Sasha Levin , netdev@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 03/16] net: caif: remove BUG_ON(dev == NULL) in caif_xmit Date: Mon, 24 May 2021 10:51:17 -0400 Message-Id: <20210524145130.2499829-3-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210524145130.2499829-1-sashal@kernel.org> References: <20210524145130.2499829-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Du Cheng [ Upstream commit 65a67792e3416f7c5d7daa47d99334cbb19a7449 ] The condition of dev == NULL is impossible in caif_xmit(), hence it is for the removal. Explanation: The static caif_xmit() is only called upon via a function pointer `ndo_start_xmit` defined in include/linux/netdevice.h: ``` struct net_device_ops { ... netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev); ... } ``` The exhausive list of call points are: ``` drivers/net/ethernet/qualcomm/rmnet/rmnet_map_command.c dev->netdev_ops->ndo_start_xmit(skb, dev); ^ ^ drivers/infiniband/ulp/opa_vnic/opa_vnic_netdev.c struct opa_vnic_adapter *adapter = opa_vnic_priv(netdev); ^ ^ return adapter->rn_ops->ndo_start_xmit(skb, netdev); // adapter would crash first ^ ^ drivers/usb/gadget/function/f_ncm.c ncm->netdev->netdev_ops->ndo_start_xmit(NULL, ncm->netdev); ^ ^ include/linux/netdevice.h static inline netdev_tx_t __netdev_start_xmit(... { return ops->ndo_start_xmit(skb, dev); ^ } const struct net_device_ops *ops = dev->netdev_ops; ^ rc = __netdev_start_xmit(ops, skb, dev, more); ^ ``` In each of the enumerated scenarios, it is impossible for the NULL-valued dev to reach the caif_xmit() without crashing the kernel earlier, therefore `BUG_ON(dev == NULL)` is rather useless, hence the removal. Cc: David S. Miller Signed-off-by: Du Cheng Link: https://lore.kernel.org/r/20210503115736.2104747-20-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/net/caif/caif_serial.c | 1 - 1 file changed, 1 deletion(-) diff --git a/drivers/net/caif/caif_serial.c b/drivers/net/caif/caif_serial.c index c2dea4916e5d..32834dad0b83 100644 --- a/drivers/net/caif/caif_serial.c +++ b/drivers/net/caif/caif_serial.c @@ -281,7 +281,6 @@ static int caif_xmit(struct sk_buff *skb, struct net_device *dev) { struct ser_device *ser; - BUG_ON(dev == NULL); ser = netdev_priv(dev); /* Send flow off once, on high water mark */ -- 2.30.2