In the Linux kernel, the following vulnerability has been resolved: clocksource/drivers/timer-sun4i: Advertise a real minimum delta sun4i_clkevt_next_event() compensates for the timer stop/start synchronization delay by programming evt…

Overview

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

clocksource/drivers/timer-sun4i: Advertise a real minimum delta

sun4i_clkevt_next_event() compensates for the timer stop/start synchronization delay by programming evt - TIMER_SYNC_TICKS into the hardware interval register. The clockevent device currently advertises TIMER_SYNC_TICKS as min_delta_ticks, so the clockevents core is allowed to call set_next_event() with evt == TIMER_SYNC_TICKS.

That programs a zero-tick interval. With oneshot/highres/nohz timer operation this can leave the next event stuck, which was observed as a boot hang on Allwinner D1 after the clockevents core started reusing forced minimum-delta events.

Advertise one extra tick instead, so the smallest event accepted by the core still programs at least one hardware tick after the synchronization compensation.

Remediation

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