Re: [PATCH net] ip6mr: fix notification device destruction

[Nikolay Aleksandrov]

On 21/04/17 20:42, Nikolay Aleksandrov wrote:
> Andrey Konovalov reported a BUG caused by the ip6mr code which is caused
> because we call unregister_netdevice_many for a device that is already
> being destroyed. In IPv4's ipmr that has been resolved by two commits
> long time ago by introducing the "notify" parameter to the delete
> function and avoiding the unregister when called from a notifier, so
> let's do the same for ip6mr.
> 
> The trace from Andrey:
> ------------[ cut here ]------------
> kernel BUG at net/core/dev.c:6813!
> invalid opcode: 0000 [#1] SMP KASAN
> Modules linked in:
> CPU: 1 PID: 1165 Comm: kworker/u4:3 Not tainted 4.11.0-rc7+ #251
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs
> 01/01/2011
> Workqueue: netns cleanup_net
> task: ffff880069208000 task.stack: ffff8800692d8000
> RIP: 0010:rollback_registered_many+0x348/0xeb0 net/core/dev.c:6813
> RSP: 0018:ffff8800692de7f0 EFLAGS: 00010297
> RAX: ffff880069208000 RBX: 0000000000000002 RCX: 0000000000000001
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88006af90569
> RBP: ffff8800692de9f0 R08: ffff8800692dec60 R09: 0000000000000000
> R10: 0000000000000006 R11: 0000000000000000 R12: ffff88006af90070
> R13: ffff8800692debf0 R14: dffffc0000000000 R15: ffff88006af90000
> FS:  0000000000000000(0000) GS:ffff88006cb00000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fe7e897d870 CR3: 00000000657e7000 CR4: 00000000000006e0
> Call Trace:
>  unregister_netdevice_many.part.105+0x87/0x440 net/core/dev.c:7881
>  unregister_netdevice_many+0xc8/0x120 net/core/dev.c:7880
>  ip6mr_device_event+0x362/0x3f0 net/ipv6/ip6mr.c:1346
>  notifier_call_chain+0x145/0x2f0 kernel/notifier.c:93
>  __raw_notifier_call_chain kernel/notifier.c:394
>  raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
>  call_netdevice_notifiers_info+0x51/0x90 net/core/dev.c:1647
>  call_netdevice_notifiers net/core/dev.c:1663
>  rollback_registered_many+0x919/0xeb0 net/core/dev.c:6841
>  unregister_netdevice_many.part.105+0x87/0x440 net/core/dev.c:7881
>  unregister_netdevice_many net/core/dev.c:7880
>  default_device_exit_batch+0x4fa/0x640 net/core/dev.c:8333
>  ops_exit_list.isra.4+0x100/0x150 net/core/net_namespace.c:144
>  cleanup_net+0x5a8/0xb40 net/core/net_namespace.c:463
>  process_one_work+0xc04/0x1c10 kernel/workqueue.c:2097
>  worker_thread+0x223/0x19c0 kernel/workqueue.c:2231
>  kthread+0x35e/0x430 kernel/kthread.c:231
>  ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430
> Code: 3c 32 00 0f 85 70 0b 00 00 48 b8 00 02 00 00 00 00 ad de 49 89
> 47 78 e9 93 fe ff ff 49 8d 57 70 49 8d 5f 78 eb 9e e8 88 7a 14 fe <0f>
> 0b 48 8b 9d 28 fe ff ff e8 7a 7a 14 fe 48 b8 00 00 00 00 00
> RIP: rollback_registered_many+0x348/0xeb0 RSP: ffff8800692de7f0
> ---[ end trace e0b29c57e9b3292c ]---
> 
> Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
> ---

+CC LKML and Linus

> Andrey could you please test with this patch applied ?
> I have run the reproducer locally and can no longer trigger the bug.
> I've made "notify" an int instead of a bool only to be closer to the ipmr
> code for easier future patches.
> 
>  net/ipv6/ip6mr.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
> index fb4546e80c82..374997d26488 100644
> --- a/net/ipv6/ip6mr.c
> +++ b/net/ipv6/ip6mr.c
> @@ -774,7 +774,8 @@ static struct net_device *ip6mr_reg_vif(struct net *net, struct mr6_table *mrt)
>   *	Delete a VIF entry
>   */
>  
> -static int mif6_delete(struct mr6_table *mrt, int vifi, struct list_head *head)
> +static int mif6_delete(struct mr6_table *mrt, int vifi, int notify,
> +		       struct list_head *head)
>  {
>  	struct mif_device *v;
>  	struct net_device *dev;
> @@ -820,7 +821,7 @@ static int mif6_delete(struct mr6_table *mrt, int vifi, struct list_head *head)
>  					     dev->ifindex, &in6_dev->cnf);
>  	}
>  
> -	if (v->flags & MIFF_REGISTER)
> +	if ((v->flags & MIFF_REGISTER) && !notify)
>  		unregister_netdevice_queue(dev, head);
>  
>  	dev_put(dev);
> @@ -1331,7 +1332,6 @@ static int ip6mr_device_event(struct notifier_block *this,
>  	struct mr6_table *mrt;
>  	struct mif_device *v;
>  	int ct;
> -	LIST_HEAD(list);
>  
>  	if (event != NETDEV_UNREGISTER)
>  		return NOTIFY_DONE;
> @@ -1340,10 +1340,9 @@ static int ip6mr_device_event(struct notifier_block *this,
>  		v = &mrt->vif6_table[0];
>  		for (ct = 0; ct < mrt->maxvif; ct++, v++) {
>  			if (v->dev == dev)
> -				mif6_delete(mrt, ct, &list);
> +				mif6_delete(mrt, ct, 1, NULL);
>  		}
>  	}
> -	unregister_netdevice_many(&list);
>  
>  	return NOTIFY_DONE;
>  }
> @@ -1552,7 +1551,7 @@ static void mroute_clean_tables(struct mr6_table *mrt, bool all)
>  	for (i = 0; i < mrt->maxvif; i++) {
>  		if (!all && (mrt->vif6_table[i].flags & VIFF_STATIC))
>  			continue;
> -		mif6_delete(mrt, i, &list);
> +		mif6_delete(mrt, i, 0, &list);
>  	}
>  	unregister_netdevice_many(&list);
>  
> @@ -1708,7 +1707,7 @@ int ip6_mroute_setsockopt(struct sock *sk, int optname, char __user *optval, uns
>  		if (copy_from_user(&mifi, optval, sizeof(mifi_t)))
>  			return -EFAULT;
>  		rtnl_lock();
> -		ret = mif6_delete(mrt, mifi, NULL);
> +		ret = mif6_delete(mrt, mifi, 0, NULL);
>  		rtnl_unlock();
>  		return ret;
>  
>