From patchwork Mon May 31 13:14:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 451241 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 61F6DC47080 for ; Mon, 31 May 2021 13:35:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 467E461935 for ; Mon, 31 May 2021 13:35:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231996AbhEaNgw (ORCPT ); Mon, 31 May 2021 09:36:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:39134 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231629AbhEaNdY (ORCPT ); Mon, 31 May 2021 09:33:24 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 779266143B; Mon, 31 May 2021 13:24:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622467470; bh=tQZdtYbWLdg5SswCUN0BLKrwEcQO7/7BTQOA25kVGX4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PcanPdL+ghM51iPoNiBY+Nng/venKJ/aIzy/vd/ZNrs0ry+lK4XhTya+AciNALLPE +wQ/PBAJOaGP6wdB88eH1n8TeeVnN6c/M4fDXSGaDZzuP6m9N+WfEeRfSUUPM6Pi74 z7bB2QNjbhcPJZSHiW10cNZ+PGnkCcL3nGEbrnjs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "David S. Miller" , Du Cheng , Sasha Levin Subject: [PATCH 4.19 078/116] net: caif: remove BUG_ON(dev == NULL) in caif_xmit Date: Mon, 31 May 2021 15:14:14 +0200 Message-Id: <20210531130642.799243355@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531130640.131924542@linuxfoundation.org> References: <20210531130640.131924542@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 a0f954f36c09..94d5ce9419ca 100644 --- a/drivers/net/caif/caif_serial.c +++ b/drivers/net/caif/caif_serial.c @@ -279,7 +279,6 @@ 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 */