overlayfs: workdir and upperdir must reside under the same mount
overlayfs: workdir and upperdir must reside under the same mount
==================================================================
BUG: KASAN: null-ptr-deref in memset include/linux/string.h:333 [inline]
BUG: KASAN: null-ptr-deref in kvm_write_guest_virt_system+0x64/0x90 arch/x86/kvm/x86.c:5030
Write of size 24 at addr 0000000000000000 by task syz-executor.2/16630

CPU: 0 PID: 16630 Comm: syz-executor.2 Not tainted 4.19.77 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 kasan_report_error mm/kasan/report.c:352 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x199/0x2ba mm/kasan/report.c:396
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x123/0x190 mm/kasan/kasan.c:267
 memset+0x24/0x40 mm/kasan/kasan.c:285
 memset include/linux/string.h:333 [inline]
 kvm_write_guest_virt_system+0x64/0x90 arch/x86/kvm/x86.c:5030
 handle_vmread+0x7fe/0xa10 arch/x86/kvm/vmx.c:8802
 vmx_handle_exit+0x276/0x16b0 arch/x86/kvm/vmx.c:10183
 vcpu_enter_guest+0x10ca/0x5ed0 arch/x86/kvm/x86.c:7756
 vcpu_run arch/x86/kvm/x86.c:7819 [inline]
 kvm_arch_vcpu_ioctl_run+0x457/0x16b0 arch/x86/kvm/x86.c:8019
 kvm_vcpu_ioctl+0x4dc/0xf90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2617
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:688
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:710
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffbf5782c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a59
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffbf57836d4
R13: 00000000004c2e48 R14: 00000000004d6978 R15: 00000000ffffffff
==================================================================