In the Linux kernel, the following vulnerability has been resolved: arm64: entry: Avoid unnecessary local_irq_disable() on kernel exit Currently, when exiting to kernel mode, we attempt involuntary preemption

Overview

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

arm64: entry: Avoid unnecessary local_irq_disable() on kernel exit

Currently, when exiting to kernel mode, we attempt involuntary preemption. The preemption logic expects IRQs to be disabled, which is why we call local_irq_disable() before attempting preemption.

However, depending on the context, local_irq_disable() may be unnecessary:

• __el1_irq(), the non-NMI EL1 IRQ path, already has IRQs disabled, so local_irq_disable() is redundant.

• irqentry_exit_to_kernel_mode_preempt() immediately returns when exiting from an NMI-like context, so calling local_irq_disable() beforehand is unnecessary work.

Furthermore, it confuses the pNMI state tracking when we are in a context with interrupts disabled and the GIC_PRIO_PSR_I_SET bit is set in the PMR, leading to a warning when CONFIG_ARM64_DEBUG_PRIORITY_MASKING=y:

 WARNING: ./arch/arm64/include/asm/irqflags.h:63 at arm64_exit_to_kernel_mode+0xb8/0xc0, CPU#40: retsnoop/31805
 CPU: 40 UID: 0 PID: 31805 Comm: retsnoop Not tainted 7.2.0-rc6-next-20260805 #7 PREEMPTLAZY
 pstate: 234013c9 (nzCv DAIF +PAN -UAO +TCO +DIT +SSBS BTYPE=--)
 pc : arm64_exit_to_kernel_mode (arch/arm64/kernel/entry-common.c:63)
 lr : el1_abort (arch/arm64/kernel/entry-common.c:323)
 pmr: 000000f0
 Call trace:
  arm64_exit_to_kernel_mode (arch/arm64/kernel/entry-common.c:63) (P)
  el1_abort (arch/arm64/kernel/entry-common.c:323)
  el1h_64_sync_handler (arch/arm64/kernel/entry-common.c:449)
  el1h_64_sync (arch/arm64/kernel/entry.S:589)
  [...]

Split arm64_exit_to_kernel_mode() into preempt, non-preempt, and dispatch parts so that we can avoid this extra work where it is not needed and avoid breaking the pNMI tracking logic.

Remediation

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