CVE-2026-98301: net: bridge: mst: move switchdev call outside rcu

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-06 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: net: bridge: mst: move switchdev call outside rcu This is a follow-up of one of sashiko's pre-existing bug reports. br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs while holding rcu_read_lock() which invokes the blocking switchdev notifier chain and may sleep. Nonzero MSTI changes come from netlink with rtnl held. Move the switchdev call before entering the rcu section and assert that rtnl is held. The call cannot be deferred because netlink needs its error and extack. Also DSA reads the old bridge MST state during the callback and checks it. A deferred callback will be late and will see the updated state.

Affected products

Linux kernel: from 6.1.93 before 6.1.189; from 6.6.33 before 6.6.158; from 6.8.12 before 6.9; from 6.9.3 before 6.10; 6.10 — fixed in 6.1.189, 6.10, 6.6.158, 6.9, 7.3

How to fix

Upgrade to a fixed version: Linux kernel 6.1.189, 6.10, 6.6.158, 6.9. Check the vendor advisory for mitigations.

References

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