CVE-2026-74726: bonding: alb: re-check primary_is_promisc under RTNL in bond_alb_monitor
bonding: alb: re-check primaryispromisc under RTNL in bondalbmonitor
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.6.152.1-1
Event History
Frequently Asked Questions
Which systems are exposed to this race condition?
Systems using Linux kernel bonding in active load balancing (ALB) mode are exposed when the active slave can be removed or changed while bond_alb_monitor() is running. The issue concerns changes made under RTNL, including RTM_DELLINK-driven slave removal.
What conditions trigger the failure?
The race requires bond_alb_monitor() to decide that it must remove promiscuous mode from the active slave, then lose RCU protection before obtaining RTNL. During that interval, the active slave must be removed or changed, causing the monitor to act on stale state.
What is the practical impact if the race occurs?
If the active slave is removed without failover, the monitor can dereference a NULL curr_active_slave and crash the kernel. If failover occurs, it can decrement the replacement slave's promiscuity counter incorrectly, leaving that interface stuck in promiscuous mode.
How can administrators recognize that the system has already hit this issue?
Affected systems may log a KASAN null-pointer dereference or general protection fault in bond_alb_monitor(), potentially followed by a kernel panic. Another indication is a replacement active slave remaining in IFF_PROMISC after a failover or slave removal.