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=-18.8 required=3.0 tests=BAYES_00,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 43E78C433E0 for ; Mon, 11 Jan 2021 13:04:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC8A5227C3 for ; Mon, 11 Jan 2021 13:04:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730113AbhAKNEE (ORCPT ); Mon, 11 Jan 2021 08:04:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:50226 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729876AbhAKNDd (ORCPT ); Mon, 11 Jan 2021 08:03:33 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E1E7622B30; Mon, 11 Jan 2021 13:02:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610370178; bh=MoUO5H4SMERM/X57okUKuEQLnXWZ9k/cq0uOJUYMSoI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hveg0i8AWJi2gXktjJtRUCSrmjpxEkrJMKTuujFjf2dWP7BH9AgPaP7N344GA4FVr dHaeDFLsaTpxCoS4PZXmIOflmA8ZfbqrYFlkQd5CMw+7+puJ8+2olGb6FdNFXFrTq+ rziHIFo19u0EhtTVf4y4wUhzLRxkIutqc36GYBpc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Krzysztof Halasa , Xie He , "David S. Miller" Subject: [PATCH 4.9 12/45] net: hdlc_ppp: Fix issues when mod_timer is called while timer is running Date: Mon, 11 Jan 2021 14:00:50 +0100 Message-Id: <20210111130034.253490852@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210111130033.676306636@linuxfoundation.org> References: <20210111130033.676306636@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xie He [ Upstream commit 1fef73597fa545c35fddc953979013882fbd4e55 ] ppp_cp_event is called directly or indirectly by ppp_rx with "ppp->lock" held. It may call mod_timer to add a new timer. However, at the same time ppp_timer may be already running and waiting for "ppp->lock". In this case, there's no need for ppp_timer to continue running and it can just exit. If we let ppp_timer continue running, it may call add_timer. This causes kernel panic because add_timer can't be called with a timer pending. This patch fixes this problem. Fixes: e022c2f07ae5 ("WAN: new synchronous PPP implementation for generic HDLC.") Cc: Krzysztof Halasa Signed-off-by: Xie He Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/wan/hdlc_ppp.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/drivers/net/wan/hdlc_ppp.c +++ b/drivers/net/wan/hdlc_ppp.c @@ -572,6 +572,13 @@ static void ppp_timer(unsigned long arg) unsigned long flags; spin_lock_irqsave(&ppp->lock, flags); + /* mod_timer could be called after we entered this function but + * before we got the lock. + */ + if (timer_pending(&proto->timer)) { + spin_unlock_irqrestore(&ppp->lock, flags); + return; + } switch (proto->state) { case STOPPING: case REQ_SENT: