==================================================================
BUG: KASAN: stack-out-of-bounds in csd_lock_record+0xd2/0xe0 kernel/smp.c:119
Read of size 8 at addr ffffc90003db75b8 by task syz-executor.2/12945

CPU: 0 PID: 12945 Comm: syz-executor.2 Not tainted 5.8.0-rc3-next-20200703-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0x5/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 csd_lock_record+0xd2/0xe0 kernel/smp.c:119
 flush_smp_call_function_queue+0x285/0x730 kernel/smp.c:391
 __sysvec_call_function_single+0x98/0x490 arch/x86/kernel/smp.c:248
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_call_function_single+0xe0/0x120 arch/x86/kernel/smp.c:243
 asm_sysvec_call_function_single+0x12/0x20 arch/x86/include/asm/idtentry.h:604
RIP: 0010:cpu_relax arch/x86/include/asm/vdso/processor.h:19 [inline]
RIP: 0010:rwsem_spin_on_owner+0x1f2/0x300 kernel/locking/rwsem.c:753
Code: 3c 2a 00 0f 85 10 01 00 00 48 83 3d 87 43 5c 08 00 0f 84 c5 00 00 00 89 c7 31 c0 0f 1f 44 00 00 84 c0 0f 85 5e ff ff ff f3 90 <e9> c7 fe ff ff 41 bc 08 00 00 00 eb 8b 80 3d 70 3f 51 09 00 0f 85
RSP: 0018:ffffc900021b7ac0 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff88804b4fc0c0 RCX: ffffffff8158bc3d
RDX: 1ffffffff136a012 RSI: 0000000000000008 RDI: 0000000000000001
RBP: ffff88803fc496b8 R08: 0000000000000000 R09: ffff888040542247
R10: ffffed10080a8448 R11: 0000000000000000 R12: ffff88803fc496c0
R13: dffffc0000000000 R14: ffff888040542240 R15: 0000000000000000
 rwsem_optimistic_spin+0xe0/0x560 kernel/locking/rwsem.c:809
 rwsem_down_read_slowpath+0x468/0xc90 kernel/locking/rwsem.c:1015
 __down_read kernel/locking/rwsem.c:1341 [inline]
 down_read+0x1eb/0x420 kernel/locking/rwsem.c:1494
 mmap_read_lock include/linux/mmap_lock.h:46 [inline]
 exit_mm kernel/exit.c:449 [inline]
 do_exit+0x696/0x2a40 kernel/exit.c:793
 do_group_exit+0x125/0x310 kernel/exit.c:904
 __do_sys_exit_group kernel/exit.c:915 [inline]
 __se_sys_exit_group kernel/exit.c:913 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:913
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:367
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cb29
Code: Bad RIP value.
RSP: 002b:00007fff931e6d88 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000000000000001e RCX: 000000000045cb29
RDX: 0000000000416721 RSI: fffffffffffffff7 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007fff931e6de0
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff931e6de0 R14: 0000000000000000 R15: 00007fff931e6df0


Memory state around the buggy address:
 ffffc90003db7480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003db7500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90003db7580: f1 f1 f1 f1 00 00 00 00 f3 f3 f3 f3 00 00 00 00
                                           ^
 ffffc90003db7600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90003db7680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================