Executive brief
A locking flaw in the Linux kernel's networking component can cause a system deadlock (freeze) when specific network LED triggers are used. This occurs when the system tries to manage network interface lights and internal network status simultaneously, leading to a circular wait for resources. An exploit could result in a complete denial of service, requiring a hard reboot to restore operations.
Technical details
An AB-BA deadlock exists in the Linux kernel when both LEDS_TRIGGER_NETDEV and LED_TRIGGER_PHY are enabled. The issue arises because LED_TRIGGER_PHY registers triggers during 'phy_attach' while holding the RTNL mutex and then attempts to acquire 'triggers_list_lock'. Conversely, LEDS_TRIGGER_NETDEV acquires 'triggers_list_lock' first and then attempts to acquire the RTNL mutex. This circular dependency results in a kernel hang. The fix involves moving 'phy_led_triggers_register' to the 'phy_probe' phase, which does not hold the RTNL mutex, thereby breaking the deadlock condition.
Affected products
- Linux Linux Kernel versions prior to 2026-03-25 patches
- Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5, V3.1.6
Timeline
- 2026-03-09: other: Patch authored
- 2026-03-25: patched: Patches committed to stable trees
- 2026-03-25: disclosed: CVE published
References
- https://git.kernel.org/stable/c/241cd64cf2e32b28ead151b1795cd8fef2b6e482
- https://git.kernel.org/stable/c/2764dcb3c35de4410f642afc62cf979727470575
- https://git.kernel.org/stable/c/2b01518eabace18f7ec8b4cafd52082303080dca
- https://git.kernel.org/stable/c/305afdd02ff3e694c165457793104710ec0728e5
- https://git.kernel.org/stable/c/c33523b8fd2d4c504ada18cd93f511f2a8f84217
- https://git.kernel.org/stable/c/c6ffc2d2338d325e1edd0c702e3ee623aa5fdc6a
- https://git.kernel.org/stable/c/c8dbdc6e380e7e96a51706db3e4b7870d8a9402d