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=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 45B1EC4363A for ; Mon, 19 Oct 2020 19:05:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E7B9822365 for ; Mon, 19 Oct 2020 19:05:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731030AbgJSTFe (ORCPT ); Mon, 19 Oct 2020 15:05:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730945AbgJSTFe (ORCPT ); Mon, 19 Oct 2020 15:05:34 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D28F4C0613CE for ; Mon, 19 Oct 2020 12:05:33 -0700 (PDT) Received: from heimdall.vpn.pengutronix.de ([2001:67c:670:205:1d::14] helo=blackshift.org) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1kUaTL-0005v5-Ro; Mon, 19 Oct 2020 21:05:31 +0200 From: Marc Kleine-Budde To: linux-can@vger.kernel.org Cc: kernel@pengutronix.de, Vincent Mailhol , Marc Kleine-Budde Subject: [net-rfc 03/16] can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ context Date: Mon, 19 Oct 2020 21:05:11 +0200 Message-Id: <20201019190524.1285319-4-mkl@pengutronix.de> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201019190524.1285319-1-mkl@pengutronix.de> References: <20201019190524.1285319-1-mkl@pengutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:205:1d::14 X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-can@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org From: Vincent Mailhol If a driver calls can_get_echo_skb() during a hardware IRQ (which is often, but not always, the case), the 'WARN_ON(in_irq)' in net/core/skbuff.c#skb_release_head_state() might be triggered, under network congestion circumstances, together with the potential risk of a NULL pointer dereference. The root cause of this issue is the call to kfree_skb() instead of dev_kfree_skb_irq() in net/core/dev.c#enqueue_to_backlog(). This patch prevents the skb to be freed within the call to netif_rx() by incrementing its reference count with skb_get(). The skb is finally freed by one of the in-irq-context safe functions: dev_consume_skb_any() or dev_kfree_skb_any(). The "any" version is used because some drivers might call can_get_echo_skb() in a normal context. The reason for this issue to occur is that initially, in the core network stack, loopback skb were not supposed to be received in hardware IRQ context. The CAN stack is an exeption. This bug was previously reported back in 2017 in [1] but the proposed patch never got accepted. While [1] directly modifies net/core/dev.c, we try to propose here a smoother modification local to CAN network stack (the assumption behind is that only CAN devices are affected by this issue). [1] http://lore.kernel.org/r/57a3ffb6-3309-3ad5-5a34-e93c3fe3614d@cetitec.com Signed-off-by: Vincent Mailhol Link: https://lore.kernel.org/r/20201002154219.4887-2-mailhol.vincent@wanadoo.fr Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface") Signed-off-by: Marc Kleine-Budde --- drivers/net/can/dev.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index b70ded3760f2..73cfcd7e9517 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -538,7 +538,11 @@ unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx) if (!skb) return 0; - netif_rx(skb); + skb_get(skb); + if (netif_rx(skb) == NET_RX_SUCCESS) + dev_consume_skb_any(skb); + else + dev_kfree_skb_any(skb); return len; } -- 2.28.0