CVE-2026-74749rseq: Prevent hard lockup on granted time slice extension

Official description

In the Linux kernel, the following vulnerability has been resolved: rseq: Prevent hard lockup on granted time slice extension __exit_to_user_mode_loop() invokes rseq_grant_timeslice_extension() with interrupts enabled. If the extension is granted it invokes hrtimer_rearm_deferred_tif() to ensure that a pending deferred hrtimer rearm is handled before exiting to user space. Though this invokes __hrtimer_rearm_deferred() which expects to be invoked with interrupts disabled as it takes hrtimer_cpu_base::lock with raw_spin_lock(). That's a livelock waiting to happen and caught by lockdep: WARNING: ./include/linux/hrtimer_rearm.h:17 at irqentry_exit, CPU#1: slice_test WARNING: inconsistent lock state inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage. Prevent this by disabling interrupts around the invocation of hrtimer_rearm_deferred_tif() in rseq_grant_timeslice_extension(). [ tglx: Massaged change log ]

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/8bbf4405050bc4f98be68082a20efa081ea8ad9b
• https://git.kernel.org/stable/c/ada54c2ba652348c590d1ace6a2f4ff77cbbf809