In the Linux kernel, the following vulnerability has been resolved: net: fix stack overflow when LRO is disabled for virtual interfaces When the virtual interface's feature is updated, it synchronizes the updated feature for its own lo…

Overview

In the Linux kernel, the following vulnerability has been resolved:

net: fix stack overflow when LRO is disabled for virtual interfaces

When the virtual interface's feature is updated, it synchronizes the updated feature for its own lower interface. This propagation logic should be worked as the iteration, not recursively. But it works recursively due to the netdev notification unexpectedly. This problem occurs when it disables LRO only for the team and bonding interface type.

   team0
     |

+------+------+-----+-----+ | | | | | team1 team2 team3 ... team200

If team0's LRO feature is updated, it generates the NETDEV_FEAT_CHANGE event to its own lower interfaces(team1 ~ team200). It is worked by netdev_sync_lower_features(). So, the NETDEV_FEAT_CHANGE notification logic of each lower interface work iteratively. But generated NETDEV_FEAT_CHANGE event is also sent to the upper interface too. upper interface(team0) generates the NETDEV_FEAT_CHANGE event for its own lower interfaces again. lower and upper interfaces receive this event and generate this event again and again. So, the stack overflow occurs.

But it is not the infinite loop issue. Because the netdev_sync_lower_features() updates features before generating the NETDEV_FEAT_CHANGE event. Already synchronized lower interfaces skip notification logic. So, it is just the problem that iteration logic is changed to the recursive unexpectedly due to the notification mechanism.

Reproducer:

ip link add team0 type team ethtool -K team0 lro on for i in {1..200} do ip link add team$i master team0 type team ethtool -K team$i lro on done

ethtool -K team0 lro off

In order to fix it, the notifier_ctx member of bonding/team is introduced.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.