From: Wei Liu <wei.liu@xxxxxxxxxx> commit ad0a6bad44758afa3b440c254a24999a0c7e35d5 upstream. We've observed crashes due to an empty cpu mask in hyperv_flush_tlb_others. Obviously the cpu mask in question is changed between the cpumask_empty call at the beginning of the function and when it is actually used later. One theory is that an interrupt comes in between and a code path ends up changing the mask. Move the check after interrupt has been disabled to see if it fixes the issue. Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> Cc: stable@xxxxxxxxxx Link: https://lore.kernel.org/r/20210105175043.28325-1-wei.liu@xxxxxxxxxx Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/hyperv/mmu.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/arch/x86/hyperv/mmu.c +++ b/arch/x86/hyperv/mmu.c @@ -66,11 +66,17 @@ static void hyperv_flush_tlb_others(cons if (!hv_hypercall_pg) goto do_native; - if (cpumask_empty(cpus)) - return; - local_irq_save(flags); + /* + * Only check the mask _after_ interrupt has been disabled to avoid the + * mask changing under our feet. + */ + if (cpumask_empty(cpus)) { + local_irq_restore(flags); + return; + } + flush_pcpu = (struct hv_tlb_flush **) this_cpu_ptr(hyperv_pcpu_input_arg);
