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Date: Thu, 07 May 2020 18:19:30 -0700 (PDT) From: David Miller <davem@...emloft.net> To: xiyou.wangcong@...il.com Cc: netdev@...r.kernel.org, syzbot+e73ceacfd8560cc8a3ca@...kaller.appspotmail.com, syzbot+c2fb6f9ddcea95ba49b5@...kaller.appspotmail.com, jarod@...hat.com, nikolay@...ulusnetworks.com, jpoimboe@...hat.com, jannh@...gle.com, jay.vosburgh@...onical.com Subject: Re: [Patch net v3] net: fix a potential recursive NETDEV_FEAT_CHANGE From: Cong Wang <xiyou.wangcong@...il.com> Date: Thu, 7 May 2020 12:19:03 -0700 > syzbot managed to trigger a recursive NETDEV_FEAT_CHANGE event > between bonding master and slave. I managed to find a reproducer > for this: > > ip li set bond0 up > ifenslave bond0 eth0 > brctl addbr br0 > ethtool -K eth0 lro off > brctl addif br0 bond0 > ip li set br0 up > > When a NETDEV_FEAT_CHANGE event is triggered on a bonding slave, > it captures this and calls bond_compute_features() to fixup its > master's and other slaves' features. However, when syncing with > its lower devices by netdev_sync_lower_features() this event is > triggered again on slaves when the LRO feature fails to change, > so it goes back and forth recursively until the kernel stack is > exhausted. > > Commit 17b85d29e82c intentionally lets __netdev_update_features() > return -1 for such a failure case, so we have to just rely on > the existing check inside netdev_sync_lower_features() and skip > NETDEV_FEAT_CHANGE event only for this specific failure case. > > Fixes: fd867d51f889 ("net/core: generic support for disabling netdev features down stack") > Reported-by: syzbot+e73ceacfd8560cc8a3ca@...kaller.appspotmail.com > Reported-by: syzbot+c2fb6f9ddcea95ba49b5@...kaller.appspotmail.com > Cc: Jarod Wilson <jarod@...hat.com> > Cc: Nikolay Aleksandrov <nikolay@...ulusnetworks.com> > Cc: Josh Poimboeuf <jpoimboe@...hat.com> > Cc: Jann Horn <jannh@...gle.com> > Reviewed-by: Jay Vosburgh <jay.vosburgh@...onical.com> > Signed-off-by: Cong Wang <xiyou.wangcong@...il.com> Applied and queued up for -stable, thanks Cong.
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