Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 13 Mar 2023 12:52:44 +0200 | Subject | Re: [PATCH net] bonding: Fix warning in default_device_exit_batch() | From | Nikolay Aleksandrov <> |
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On 13/03/2023 11:35, Shigeru Yoshida wrote: > Hi Nik, > > On Sun, Mar 12, 2023 at 10:58:18PM +0200, Nikolay Aleksandrov wrote: >> On 12/03/2023 17:21, Shigeru Yoshida wrote: >>> syzbot reported warning in default_device_exit_batch() like below [1]: >>> >>> WARNING: CPU: 1 PID: 56 at net/core/dev.c:10867 unregister_netdevice_many_notify+0x14cf/0x19f0 net/core/dev.c:10867 >>> ... >>> Call Trace: >>> <TASK> >>> unregister_netdevice_many net/core/dev.c:10897 [inline] >>> default_device_exit_batch+0x451/0x5b0 net/core/dev.c:11350 >>> ops_exit_list+0x125/0x170 net/core/net_namespace.c:174 >>> cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:613 >>> process_one_work+0x9bf/0x1820 kernel/workqueue.c:2390 >>> worker_thread+0x669/0x1090 kernel/workqueue.c:2537 >>> kthread+0x2e8/0x3a0 kernel/kthread.c:376 >>> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308 >>> </TASK> >>> >>> For bond devices which also has a master device, IFF_SLAVE flag is >>> cleared at err_undo_flags label in bond_enslave() if it is not >>> ARPHRD_ETHER type. In this case, __bond_release_one() is not called >>> when bond_netdev_event() received NETDEV_UNREGISTER event. This >>> causes the above warning. >>> >>> This patch fixes this issue by setting IFF_SLAVE flag at >>> err_undo_flags label in bond_enslave() if the bond device has a master >>> device. >>> >> >> The proper way is to check if the bond device had the IFF_SLAVE flag before the >> ether_setup() call which clears it, and restore it after. >> >>> Fixes: 7d5cd2ce5292 ("bonding: correctly handle bonding type change on enslave failure") >>> Cc: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> >>> Link: https://syzkaller.appspot.com/bug?id=391c7b1f6522182899efba27d891f1743e8eb3ef [1] >>> Reported-by: syzbot+9dfc3f3348729cc82277@syzkaller.appspotmail.com >>> Signed-off-by: Shigeru Yoshida <syoshida@redhat.com> >>> --- >>> drivers/net/bonding/bond_main.c | 2 ++ >>> include/net/bonding.h | 5 +++++ >>> 2 files changed, 7 insertions(+) >>> >>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c >>> index 00646aa315c3..1a8b59e1468d 100644 >>> --- a/drivers/net/bonding/bond_main.c >>> +++ b/drivers/net/bonding/bond_main.c >>> @@ -2291,6 +2291,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev, >>> dev_close(bond_dev); >>> ether_setup(bond_dev); >>> bond_dev->flags |= IFF_MASTER; >>> + if (bond_has_master(bond)) >>> + bond_dev->flags |= IFF_SLAVE; >>> bond_dev->priv_flags &= ~IFF_TX_SKB_SHARING; >>> } >>> } >>> diff --git a/include/net/bonding.h b/include/net/bonding.h >>> index ea36ab7f9e72..ed0b49501fad 100644 >>> --- a/include/net/bonding.h >>> +++ b/include/net/bonding.h >>> @@ -57,6 +57,11 @@ >>> >>> #define bond_has_slaves(bond) !list_empty(bond_slave_list(bond)) >>> >>> +/* master list primitives */ >>> +#define bond_master_list(bond) (&(bond)->dev->adj_list.upper) >>> + >>> +#define bond_has_master(bond) !list_empty(bond_master_list(bond)) >>> + >> >> This is not the proper way to check for a master device. >> >>> /* IMPORTANT: bond_first/last_slave can return NULL in case of an empty list */ >>> #define bond_first_slave(bond) \ >>> (bond_has_slaves(bond) ? \ >> >> The device flags are wrong because of ether_setup() which clears IFF_SLAVE, we should >> just check if it was present before and restore it after the ether_setup() call. > > Thank you so much for your comment! I understand your point, and > agree that your approach must resolve the issue. > > BTW, do you mean there is a case where a device has IFF_SLAVE flag but > the upper list is empty? I thought a device with IFF_SLAVE flag has a > master device in the upper list (that is why I took the above way.) >
Hi Shigeru, No, that's not what I meant. It's the opposite actually, you may have an upper list but you don't have a "master" device or slave flag set. Yes, you can say that if a device has IFF_SLAVE set, then it must have a master upper device but that's not what you're checking for, you've reversed that logic to check for an upper device instead and assume there's a IFF_SLAVE flag set (which may not be true). For an upper device to be considered a "master" device, it must have the master bool set to true in its netdev_adjacent structure. We already have helpers to check for master devices and to retrieve them, e.g. check netdev_master_upper_dev_get* in net/core/dev.c
The most robust way to fix it is to check if the flag was there prior to the ether_setup() call and restore it after, also to leave a nice comment about all of this. :)
> Thanks, > Shigeru >
Cheers, Nik
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