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 71566C433EF for ; Fri, 28 Jan 2022 07:44:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345613AbiA1HoI (ORCPT ); Fri, 28 Jan 2022 02:44:08 -0500 Received: from mo4-p00-ob.smtp.rzone.de ([85.215.255.24]:38719 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345403AbiA1HoI (ORCPT ); Fri, 28 Jan 2022 02:44:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1643355837; s=strato-dkim-0002; d=hartkopp.net; h=Message-Id:Date:Subject:Cc:To:From:Cc:Date:From:Subject:Sender; bh=ILmWpONKz/8ibcQzKN1YtBaQrZ3n3cjfdkSgSRkAx5M=; b=izCqrHtsR9P/HktP6t5kMnZzBNxcjHKms1OuHvdb7HHxxQOPEDegQ31gJoSOZhHYV2 GHZsJ+1n68Kt9EwuxXi9Hge8GGq85qerc6Y3TClkWgYNTdi0/feQJ5KEXZ5idm5rIwab ALjtqDsJuZnVcusydFMoPvYtBYuFDSzuneX1y2cNMCJgexg8euX6s0LRgGNgraifu58Q k69w5McYsSBK4ayDI/0u51qvszOzykXpN++ZGnTdbAqix6l81bKrwb0Ihc+7TrFKEaBH Kp4pXW08okuw5qsRP3/I8lGei3vuLBTstUS5gMC8XCmhjhez2+O1iEzrrdvZq7g4DudF gzNA== Authentication-Results: strato.com; dkim=none X-RZG-AUTH: ":P2MHfkW8eP4Mre39l357AZT/I7AY/7nT2yrDxb8mjGrp7owjzFK3JbFk1mS/xvEBL7X5sbo3UIh9IyLecSWJafUvprl4" X-RZG-CLASS-ID: mo00 Received: from silver.lan by smtp.strato.de (RZmta 47.38.0 AUTH) with ESMTPSA id zaacbfy0S7hvPsn (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Fri, 28 Jan 2022 08:43:57 +0100 (CET) From: Oliver Hartkopp To: netdev@vger.kernel.org, linux-can@vger.kernel.org, william.xuanziyang@huawei.com Cc: Oliver Hartkopp , syzbot+4c63f36709a642f801c5@syzkaller.appspotmail.com Subject: [RFC][PATCH v2] can: isotp: fix CAN frame reception race in isotp_rcv() Date: Fri, 28 Jan 2022 08:43:27 +0100 Message-Id: <20220128074327.52229-1-socketcan@hartkopp.net> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org When receiving a CAN frame the current code logic does not consider concurrently receiving processes which do not show up in real world usage. Ziyang Xuan writes: The following syz problem is one of the scenarios. so->rx.len is changed by isotp_rcv_ff() during isotp_rcv_cf(), so->rx.len equals 0 before alloc_skb() and equals 4096 after alloc_skb(). That will trigger skb_over_panic() in skb_put(). ======================================================= CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc8-syzkaller #0 RIP: 0010:skb_panic+0x16c/0x16e net/core/skbuff.c:113 Call Trace: skb_over_panic net/core/skbuff.c:118 [inline] skb_put.cold+0x24/0x24 net/core/skbuff.c:1990 isotp_rcv_cf net/can/isotp.c:570 [inline] isotp_rcv+0xa38/0x1e30 net/can/isotp.c:668 deliver net/can/af_can.c:574 [inline] can_rcv_filter+0x445/0x8d0 net/can/af_can.c:635 can_receive+0x31d/0x580 net/can/af_can.c:665 can_rcv+0x120/0x1c0 net/can/af_can.c:696 __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5465 __netif_receive_skb+0x24/0x1b0 net/core/dev.c:5579 Therefore we make sure the state changes and data structures stay consistent at CAN frame reception time by adding a spin_lock in isotp_rcv(). This fixes the issue reported by syzkaller but does not affect real world operation. Link: https://lore.kernel.org/linux-can/d7e69278-d741-c706-65e1-e87623d9a8e8@huawei.com/T/ Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol") Reported-by: syzbot+4c63f36709a642f801c5@syzkaller.appspotmail.com Reported-by: Ziyang Xuan Signed-off-by: Oliver Hartkopp --- net/can/isotp.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/net/can/isotp.c b/net/can/isotp.c index 02cbcb2ecf0d..b5ba1a9a9e3b 100644 --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -54,10 +54,11 @@ */ #include #include #include +#include #include #include #include #include #include @@ -143,10 +144,11 @@ struct isotp_sock { u32 force_tx_stmin; u32 force_rx_stmin; struct tpcon rx, tx; struct list_head notifier; wait_queue_head_t wait; + spinlock_t rx_lock; }; static LIST_HEAD(isotp_notifier_list); static DEFINE_SPINLOCK(isotp_notifier_lock); static struct isotp_sock *isotp_busy_notifier; @@ -613,10 +615,19 @@ static void isotp_rcv(struct sk_buff *skb, void *data) if (ae && cf->data[0] != so->opt.rx_ext_address) return; n_pci_type = cf->data[ae] & 0xF0; + /* Make sure the state changes and data structures stay consistent at + * CAN frame reception time. This locking is not needed in real world + * use cases but the inconsistency can be triggered with syzkaller. + * + * To not lock up the softirq just drop the frame in syzcaller case. + */ + if (!spin_trylock(&so->rx_lock)) + return; + if (so->opt.flags & CAN_ISOTP_HALF_DUPLEX) { /* check rx/tx path half duplex expectations */ if ((so->tx.state != ISOTP_IDLE && n_pci_type != N_PCI_FC) || (so->rx.state != ISOTP_IDLE && n_pci_type == N_PCI_FC)) return; @@ -666,10 +677,12 @@ static void isotp_rcv(struct sk_buff *skb, void *data) case N_PCI_CF: /* rx path: consecutive frame */ isotp_rcv_cf(sk, cf, ae, skb); break; } + + spin_unlock(&so->rx_lock); } static void isotp_fill_dataframe(struct canfd_frame *cf, struct isotp_sock *so, int ae, int off) { @@ -1442,10 +1455,11 @@ static int isotp_init(struct sock *sk) so->rxtimer.function = isotp_rx_timer_handler; hrtimer_init(&so->txtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_SOFT); so->txtimer.function = isotp_tx_timer_handler; init_waitqueue_head(&so->wait); + spin_lock_init(&so->rx_lock); spin_lock(&isotp_notifier_lock); list_add_tail(&so->notifier, &isotp_notifier_list); spin_unlock(&isotp_notifier_lock); -- 2.30.2