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: 17b85d29e82c ("net/core: revert "net: fix __netdev_update_features
return.." and add comment")
Reported-by: syzbot+e73ceacfd8560cc8a...@syzkaller.appspotmail.com
Reported-by: syzbot+c2fb6f9ddcea95ba4...@syzkaller.appspotmail.com
Cc: Nikolay Aleksandrov <niko...@cumulusnetworks.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Jay Vosburgh <j.vosbu...@gmail.com>
Cc: Jann Horn <ja...@google.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
net/core/dev.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 522288177bbd..6d327b7aa813 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8907,11 +8907,13 @@ static void netdev_sync_lower_features(struct
net_device *upper,
netdev_dbg(upper, "Disabling feature %pNF on lower dev
%s.\n",
&feature, lower->name);
lower->wanted_features &= ~feature;
- netdev_update_features(lower);
+ __netdev_update_features(lower);
if (unlikely(lower->features & feature))
netdev_WARN(upper, "failed to disable %pNF on
%s!\n",
&feature, lower->name);
+ else
+ netdev_features_change(lower);
}
}
}
--
2.26.2
