linux-kernel - Re: drivers/vhost/net.c:1010 vhost_net_rx_peek_head_len() error: double unlocked 'sk->sk_receive

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Message-ID: <20200810083313-mutt-send-email-mst@kernel.org>
Date:   Mon, 10 Aug 2020 08:33:48 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     kernel test robot <lkp@...el.com>
Cc:     Jason Wang <jasowang@...hat.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: drivers/vhost/net.c:1010 vhost_net_rx_peek_head_len() error:
 double unlocked 'sk->sk_receive_queue.lock' (orig line 1002)

On Sat, Aug 08, 2020 at 03:37:07PM +0800, kernel test robot wrote:
> Hi Jason,
> 
> First bad commit (maybe != root cause):
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   449dc8c97089a6e09fb2dac4d92b1b7ac0eb7c1e
> commit: 20c384f1ea1a0bc7320bc445c72dd02d2970d594 vhost: refine vhost and vringh kconfig
> date:   4 months ago
> config: arm-randconfig-m031-20200808 (attached as .config)
> compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> New smatch warnings:
> drivers/vhost/net.c:1010 vhost_net_rx_peek_head_len() error: double unlocked 'sk->sk_receive_queue.lock' (orig line 1002)
> drivers/vhost/net.c:1010 vhost_net_rx_peek_head_len() error: double unlocked 'sk->sk_receive_queue.lock' (orig line 1002)

Weird. Can't figure out where the double unlock is ...


> Old smatch warnings:
> drivers/vhost/net.c:1528 vhost_net_set_backend() warn: passing a valid pointer to 'PTR_ERR'

this stumped me too...

> vim +1010 drivers/vhost/net.c
> 
> 8dd014adfea6f17 David Stevens   2010-07-27   994  
> be294a51adfc1e1 Toshiaki Makita 2018-07-03   995  static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
> be294a51adfc1e1 Toshiaki Makita 2018-07-03   996  				      bool *busyloop_intr)
> 030881372460654 Jason Wang      2016-03-04   997  {
> 28b9b33b983f4de Toshiaki Makita 2018-07-03   998  	struct vhost_net_virtqueue *rnvq = &net->vqs[VHOST_NET_VQ_RX];
> 28b9b33b983f4de Toshiaki Makita 2018-07-03   999  	struct vhost_net_virtqueue *tnvq = &net->vqs[VHOST_NET_VQ_TX];
> 6369fec5be0aad4 Toshiaki Makita 2018-07-03  1000  	struct vhost_virtqueue *rvq = &rnvq->vq;
> 28b9b33b983f4de Toshiaki Makita 2018-07-03  1001  	struct vhost_virtqueue *tvq = &tnvq->vq;
> 28b9b33b983f4de Toshiaki Makita 2018-07-03 @1002  	int len = peek_head_len(rnvq, sk);
> 030881372460654 Jason Wang      2016-03-04  1003  
> dc151282bbdaed0 Tonghao Zhang   2018-09-25  1004  	if (!len && rvq->busyloop_timeout) {
> f5a4941aa6d190e Jason Wang      2018-05-29  1005  		/* Flush batched heads first */
> 09c3248938c3e3b Jason Wang      2018-07-20  1006  		vhost_net_signal_used(rnvq);
> 030881372460654 Jason Wang      2016-03-04  1007  		/* Both tx vq and rx socket were polled here */
> dc151282bbdaed0 Tonghao Zhang   2018-09-25  1008  		vhost_net_busy_poll(net, rvq, tvq, busyloop_intr, true);
> 030881372460654 Jason Wang      2016-03-04  1009  
> 28b9b33b983f4de Toshiaki Makita 2018-07-03 @1010  		len = peek_head_len(rnvq, sk);
> 030881372460654 Jason Wang      2016-03-04  1011  	}
> 030881372460654 Jason Wang      2016-03-04  1012  
> 030881372460654 Jason Wang      2016-03-04  1013  	return len;
> 030881372460654 Jason Wang      2016-03-04  1014  }
> 030881372460654 Jason Wang      2016-03-04  1015  
> 
> :::::: The code at line 1010 was first introduced by commit
> :::::: 28b9b33b983f4de3ce9e660e3efe1e08adabf779 vhost_net: Rename local variables in vhost_net_rx_peek_head_len
> 
> :::::: TO: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
> :::::: CC: David S. Miller <davem@...emloft.net>
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org