Subject: Re: [PATCH 2/2] virtio: delete napi structures from netdev before releasing memory

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 5 Dec 2013 16:53:39 +0200

On Thu, Dec 05, 2013 at 06:36:21PM +0400, Andrey Vagin wrote:
> free_netdev calls netif_napi_del too, but it's too late, because napi
> structures are placed on vi->rq. netif_napi_add() is called from
> virtnet_alloc_queues.
> 
> general protection fault: 0000 [#1] SMP
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in: ip6table_filter ip6_tables iptable_filter ip_tables virtio_balloon pcspkr virtio_net(-) i2c_pii
> CPU: 1 PID: 347 Comm: rmmod Not tainted 3.13.0-rc2+ #171
> Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> task: ffff8800b779c420 ti: ffff8800379e0000 task.ti: ffff8800379e0000
> RIP: 0010:[<ffffffff81322e19>]  [<ffffffff81322e19>] __list_del_entry+0x29/0xd0
> RSP: 0018:ffff8800379e1dd0  EFLAGS: 00010a83
> RAX: 6b6b6b6b6b6b6b6b RBX: ffff8800379c2fd0 RCX: dead000000200200
> RDX: 6b6b6b6b6b6b6b6b RSI: 0000000000000001 RDI: ffff8800379c2fd0
> RBP: ffff8800379e1dd0 R08: 0000000000000001 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: ffff8800379c2f90
> R13: ffff880037839160 R14: 0000000000000000 R15: 00000000013352f0
> FS:  00007f1400e34740(0000) GS:ffff8800bfb00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 00007f464124c763 CR3: 00000000b68cf000 CR4: 00000000000006e0
> Stack:
>  ffff8800379e1df0 ffffffff8155beab 6b6b6b6b6b6b6b2b ffff8800378391c0
>  ffff8800379e1e18 ffffffff8156499b ffff880037839be0 ffff880037839d20
>  ffff88003779d3f0 ffff8800379e1e38 ffffffffa003477c ffff88003779d388
> Call Trace:
>  [<ffffffff8155beab>] netif_napi_del+0x1b/0x80
>  [<ffffffff8156499b>] free_netdev+0x8b/0x110
>  [<ffffffffa003477c>] virtnet_remove+0x7c/0x90 [virtio_net]
>  [<ffffffff813ae323>] virtio_dev_remove+0x23/0x80
>  [<ffffffff813f62ef>] __device_release_driver+0x7f/0xf0
>  [<ffffffff813f6ca0>] driver_detach+0xc0/0xd0
>  [<ffffffff813f5f28>] bus_remove_driver+0x58/0xd0
>  [<ffffffff813f72ec>] driver_unregister+0x2c/0x50
>  [<ffffffff813ae65e>] unregister_virtio_driver+0xe/0x10
>  [<ffffffffa0036942>] virtio_net_driver_exit+0x10/0x6ce [virtio_net]
>  [<ffffffff810d7cf2>] SyS_delete_module+0x172/0x220
>  [<ffffffff810a732d>] ? trace_hardirqs_on+0xd/0x10
>  [<ffffffff810f5d4c>] ? __audit_syscall_entry+0x9c/0xf0
>  [<ffffffff81677f69>] system_call_fastpath+0x16/0x1b
> Code: 00 00 55 48 8b 17 48 b9 00 01 10 00 00 00 ad de 48 8b 47 08 48 89 e5 48 39 ca 74 29 48 b9 00 02 20 00 00 00
> RIP  [<ffffffff81322e19>] __list_del_entry+0x29/0xd0
>  RSP <ffff8800379e1dd0>
> ---[ end trace d5931cd3f87c9763 ]---
> 
> Fixes: 986a4f4d452d (virtio_net: multiqueue support)
> Cc: Rusty Russell <[email-masked]>
> Cc: "Michael S. Tsirkin" <[email-masked]>
> Signed-off-by: Andrey Vagin <[email-masked]>

Acked-by: Michael S. Tsirkin <[email-masked]>

This is needed for stable.

> ---
>  drivers/net/virtio_net.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 930039a..c293764 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1367,6 +1367,11 @@ static void virtnet_config_changed(struct virtio_device *vdev)
>  
>  static void virtnet_free_queues(struct virtnet_info *vi)
>  {
> +	int i;
> +
> +	for (i = 0; i < vi->max_queue_pairs; i++)
> +		netif_napi_del(&vi->rq[i].napi);
> +
>  	kfree(vi->rq);
>  	kfree(vi->sq);
>  }
> -- 
> 1.8.3.1