In the Linux kernel, the following vulnerability has been resolved: arm64: hibernate: mask DAIF before restoring hibernated kernel The arm

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

arm64: hibernate: mask DAIF before restoring hibernated kernel

The arm64 hibernate code manages the exception masking in an unsound
way, leading to potential crashes and/or warnings during resume.

When a hibernation image is saved in swsusp_arch_suspend(), all DAIF
exceptions are masked (by virtue of local_daif_save()), and the
suspended image is saved assuming that all DAIF exceptions will remain
masked when the image is restored.

When a hibernation image is resumed by swsusp_arch_resume(), only
interrupts are masked (by virtue of local_irq_disable() in
resume_target_kernel()). When pseudo-NMI is enabled the DAIF.IF bits
will be clear, and regardless of pseudo-NMI the DAIF.DA bits will be
clear.

This means that there are two problems:

(1) It is possible to take Debug, SError, or pseudo-NMI exceptions
during the resume process. This is unsafe, as during the resume
process both the old ane new kernels will tranisently be in an
inconsistent state, and swsusp_arch_suspend_exit() won't retain
an executable mapping of any exception vectors.

 1Any exception taken here will be fatal and silent.

(2) When re-entering the resumed kernel, some DAIF bits will be clear
unexpectedly. This permits Debug, SError, or pseudo-NMI exceptions
to be taken for a short period while the resumed kernel is not yet
in a consistent state.

 1This is detected by CONFIG_ARM64_DEBUG_PRIORITY_MASKING.

Avoid these issues by masking all DAIF exceptions during resume.