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=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 422C0C433DB for ; Mon, 11 Jan 2021 13:06:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 074B82225E for ; Mon, 11 Jan 2021 13:06:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728072AbhAKNGn (ORCPT ); Mon, 11 Jan 2021 08:06:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:53036 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730340AbhAKNFk (ORCPT ); Mon, 11 Jan 2021 08:05:40 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7844C2251F; Mon, 11 Jan 2021 13:04:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610370299; bh=MoUO5H4SMERM/X57okUKuEQLnXWZ9k/cq0uOJUYMSoI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NPbdURtz1r6li0wyeEJpdBqrkZ27p6SZwqzLRsgbETd+QePQ+O38pVSA4ax7c6Y4E fp0IW4EnKagNqVS4cRoMJ4OVpud/DRvOOp4iRD8/E/p3rxzHiGwFD5N67VwklogTn7 o2seioBKz9Pzwm97yUHDHSOfmNaOvPAjSAUTQUn0= 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 4.14 19/57] net: hdlc_ppp: Fix issues when mod_timer is called while timer is running Date: Mon, 11 Jan 2021 14:01:38 +0100 Message-Id: <20210111130034.651758372@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210111130033.715773309@linuxfoundation.org> References: <20210111130033.715773309@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: