On 04/04/26 06:31, Ritesh Harjani (IBM) wrote:
Sourabh Jain <[email protected]> writes:The kexec sequence invokes enter_vmx_ops() via copy_page() with the MMU disabled. In this context, code must not rely on normal virtual address translations or trigger page faults. With KASAN enabled, functions get instrumented and may access shadow memory using regular address translation. When executed with the MMU off, this can lead to page faults (bad_page_fault) from which the kernel cannot recover in the kexec path, resulting in a hang. The kexec path sets preempt_count to HARDIRQ_OFFSET before entering the MMU-off copy sequence. current_thread_info()->preempt_count = HARDIRQ_OFFSET kexec_sequence(..., copy_with_mmu_off = 1) -> kexec_copy_flush(image) copy_segments() -> copy_page(dest, addr) bl enter_vmx_ops() if (in_interrupt()) return 0 beq .Lnonvmx_copy Since kexec sets preempt_count to HARDIRQ_OFFSET, in_interrupt() evaluates to true and enter_vmx_ops() returns early. As in_interrupt() (and preempt_count()) are always inlined, mark enter_vmx_ops() with __no_sanitize_address to avoid KASAN instrumentation and shadow memory access with MMU disabled, helping kexec boot fine with KASAN enabled.Nice! LGTM. Please feel free to add: Reviewed-by: Ritesh Harjani (IBM) <[email protected]>
Thanks, Ritesh! Will add your Reviewed-by tag in the next version. - Sourabh Jain
