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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98EA2C636D6 for ; Tue, 7 Feb 2023 13:13:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232431AbjBGNNG (ORCPT ); Tue, 7 Feb 2023 08:13:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232361AbjBGNMs (ORCPT ); Tue, 7 Feb 2023 08:12:48 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5E792138 for ; Tue, 7 Feb 2023 05:11:51 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 5925CCE1D86 for ; Tue, 7 Feb 2023 13:11:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FF9EC433EF; Tue, 7 Feb 2023 13:11:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1675775495; bh=gYGHPw3ENpPznyq1j2cJTE//ba/G0A0Hp6On5NHJEvo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r2SH93k4tausJjWEAsuEDNE6lw7y2bO2va7v3LHfNTTi8Q8nfeVZx8QwkybiasotG gowlYu4jxuWeuL9FahKdl8u8FbgYKw0St4bKsTgP99ou47S/AUftaFF8pi+wfIU+iC e9hGqdEYsIiwm9oECOHyrQgJaYmu1oJRlZuwpVAo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+9981a614060dcee6eeca@syzkaller.appspotmail.com, Ziyang Xuan , Oleksij Rempel , Marc Kleine-Budde , Sasha Levin Subject: [PATCH 5.15 042/120] can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate Date: Tue, 7 Feb 2023 13:56:53 +0100 Message-Id: <20230207125620.562068509@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230207125618.699726054@linuxfoundation.org> References: <20230207125618.699726054@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Ziyang Xuan [ Upstream commit d0553680f94c49bbe0e39eb50d033ba563b4212d ] The conclusion "j1939_session_deactivate() should be called with a session ref-count of at least 2" is incorrect. In some concurrent scenarios, j1939_session_deactivate can be called with the session ref-count less than 2. But there is not any problem because it will check the session active state before session putting in j1939_session_deactivate_locked(). Here is the concurrent scenario of the problem reported by syzbot and my reproduction log. cpu0 cpu1 j1939_xtp_rx_eoma j1939_xtp_rx_abort_one j1939_session_get_by_addr [kref == 2] j1939_session_get_by_addr [kref == 3] j1939_session_deactivate [kref == 2] j1939_session_put [kref == 1] j1939_session_completed j1939_session_deactivate WARN_ON_ONCE(kref < 2) ===================================================== WARNING: CPU: 1 PID: 21 at net/can/j1939/transport.c:1088 j1939_session_deactivate+0x5f/0x70 CPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 5.14.0-rc7+ #32 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014 RIP: 0010:j1939_session_deactivate+0x5f/0x70 Call Trace: j1939_session_deactivate_activate_next+0x11/0x28 j1939_xtp_rx_eoma+0x12a/0x180 j1939_tp_recv+0x4a2/0x510 j1939_can_recv+0x226/0x380 can_rcv_filter+0xf8/0x220 can_receive+0x102/0x220 ? process_backlog+0xf0/0x2c0 can_rcv+0x53/0xf0 __netif_receive_skb_one_core+0x67/0x90 ? process_backlog+0x97/0x2c0 __netif_receive_skb+0x22/0x80 Fixes: 0c71437dd50d ("can: j1939: j1939_session_deactivate(): clarify lifetime of session object") Reported-by: syzbot+9981a614060dcee6eeca@syzkaller.appspotmail.com Signed-off-by: Ziyang Xuan Acked-by: Oleksij Rempel Link: https://lore.kernel.org/all/20210906094200.95868-1-william.xuanziyang@huawei.com Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin --- net/can/j1939/transport.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index 55f29c9f9e08..4177e9617070 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -1092,10 +1092,6 @@ static bool j1939_session_deactivate(struct j1939_session *session) bool active; j1939_session_list_lock(priv); - /* This function should be called with a session ref-count of at - * least 2. - */ - WARN_ON_ONCE(kref_read(&session->kref) < 2); active = j1939_session_deactivate_locked(session); j1939_session_list_unlock(priv); -- 2.39.0