Executive brief
A deadlock vulnerability exists in the Linux kernel's m68k Natfeat console driver. When the console system attempts to display active console information, it can cause the kernel to hang indefinitely due to conflicting lock acquisitions. This results in system unresponsiveness and potential service outages on affected m68k systems.
Technical details
The vulnerability is a deadlock condition in the nfcon_device() function in arch/m68k/emu/nfcon.c. The root cause is that show_cons_active() calls the .device() method while holding console_list_lock, but nfcon_device() calls console_is_registered() which attempts to acquire the same console_list_lock, leading to a recursive lock acquisition deadlock. The fix removes the unnecessary console_is_registered() check, since the function should only be called when the console is already registered. The deadlock can be triggered through normal console enumeration operations and requires no special privileges or user interaction.
Affected products
- Linux Linux kernel 5.0+
Timeline
- 2026-09-17: disclosed
- 2026-08-15: patched: Upstream fix merged
- 2026-09-14: patched: Stable kernel backport