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Subject: Re: [PATCH net v2 1/2] can: isotp: add result check for
 wait_event_interruptible()
To:     Ziyang Xuan <william.xuanziyang@huawei.com>, mkl@pengutronix.de
Cc:     davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1633764159.git.william.xuanziyang@huawei.com>
 <10ca695732c9dd267c76a3c30f37aefe1ff7e32f.1633764159.git.william.xuanziyang@huawei.com>
From:   Oliver Hartkopp <socketcan@hartkopp.net>
Message-ID: <d811c05a-59f6-947b-7c1b-dfec1a69d42d@hartkopp.net>
Date:   Mon, 11 Oct 2021 21:10:46 +0200
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On 09.10.21 09:40, Ziyang Xuan wrote:
> Using wait_event_interruptible() to wait for complete transmission,
> but do not check the result of wait_event_interruptible() which can
> be interrupted. It will result in tx buffer has multiple accessers
> and the later process interferes with the previous process.
> 
> Following is one of the problems reported by syzbot.
> 
> =============================================================
> WARNING: CPU: 0 PID: 0 at net/can/isotp.c:840 isotp_tx_timer_handler+0x2e0/0x4c0
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.13.0-rc7+ #68
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014
> RIP: 0010:isotp_tx_timer_handler+0x2e0/0x4c0
> Call Trace:
>   <IRQ>
>   ? isotp_setsockopt+0x390/0x390
>   __hrtimer_run_queues+0xb8/0x610
>   hrtimer_run_softirq+0x91/0xd0
>   ? rcu_read_lock_sched_held+0x4d/0x80
>   __do_softirq+0xe8/0x553
>   irq_exit_rcu+0xf8/0x100
>   sysvec_apic_timer_interrupt+0x9e/0xc0
>   </IRQ>
>   asm_sysvec_apic_timer_interrupt+0x12/0x20
> 
> Add result check for wait_event_interruptible() in isotp_sendmsg()
> to avoid multiple accessers for tx buffer.
> 
> Reported-by: syzbot+78bab6958a614b0c80b9@syzkaller.appspotmail.com
> Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>

Many thanks!
Oliver

> ---
>   net/can/isotp.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/can/isotp.c b/net/can/isotp.c
> index caaa532ece94..2ac29c2b2ca6 100644
> --- a/net/can/isotp.c
> +++ b/net/can/isotp.c
> @@ -865,7 +865,9 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
>   			return -EAGAIN;
>   
>   		/* wait for complete transmission of current pdu */
> -		wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
> +		err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE);
> +		if (err)
> +			return err;
>   	}
>   
>   	if (!size || size > MAX_MSG_LENGTH)
>