On Mon, Oct 05, 2020 at 07:37:38PM -0400, Sasha Levin wrote: > cpumask can change underneath us, which is generally safe except when we > call into hv_cpu_number_to_vp_number(): if cpumask ends up empty we pass > num_cpu_possible() into hv_cpu_number_to_vp_number(), causing it to read > garbage. As reported by KASAN: > > [ 83.504763] BUG: KASAN: slab-out-of-bounds in hyperv_flush_tlb_others (include/asm-generic/mshyperv.h:128 arch/x86/hyperv/mmu.c:112) > [ 83.908636] Read of size 4 at addr ffff888267c01370 by task kworker/u8:2/106 > [ 84.196669] CPU: 0 PID: 106 Comm: kworker/u8:2 Tainted: G W 5.4.60 #1 > [ 84.196669] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS 090008 12/07/2018 > [ 84.196669] Workqueue: writeback wb_workfn (flush-8:0) > [ 84.196669] Call Trace: > [ 84.196669] dump_stack (lib/dump_stack.c:120) > [ 84.196669] print_address_description.constprop.0 (mm/kasan/report.c:375) > [ 84.196669] __kasan_report.cold (mm/kasan/report.c:507) > [ 84.196669] kasan_report (arch/x86/include/asm/smap.h:71 mm/kasan/common.c:635) > [ 84.196669] hyperv_flush_tlb_others (include/asm-generic/mshyperv.h:128 arch/x86/hyperv/mmu.c:112) > [ 84.196669] flush_tlb_mm_range (arch/x86/include/asm/paravirt.h:68 arch/x86/mm/tlb.c:798) > [ 84.196669] ptep_clear_flush (arch/x86/include/asm/tlbflush.h:586 mm/pgtable-generic.c:88) > What is the easiest way to reproduce this? Just enable KASAN in the guest and run it normally? I want to have a chance to verify my earlier reply. Thanks, Wei.
