From: Cong Wang <xiyou.wangc...@gmail.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+e73ceacfd8560cc8a...@syzkaller.appspotmail.com
> Reported-by: syzbot+c2fb6f9ddcea95ba4...@syzkaller.appspotmail.com
> Cc: Jarod Wilson <ja...@redhat.com>
> Cc: Nikolay Aleksandrov <niko...@cumulusnetworks.com>
> Cc: Josh Poimboeuf <jpoim...@redhat.com>
> Cc: Jann Horn <ja...@google.com>
> Reviewed-by: Jay Vosburgh <jay.vosbu...@canonical.com>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
Applied and queued up for -stable, thanks Cong.
