Re: KASAN: stack-out-of-bounds Read in csd_lock_record

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    9e50b94b Add linux-next specific files for 20200703
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1224dc83100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f99cc0faa1476ed6
dashboard link: https://syzkaller.appspot.com/bug?extid=0f719294463916a3fc0e
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=170442d5100000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162ef66d100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0f719294463916a3fc0e@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: stack-out-of-bounds in csd_lock_record+0xd2/0xe0 kernel/smp.c:119
Read of size 8 at addr ffffc900016d75f8 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 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:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: ff 4c 89 ef e8 33 30 c7 f9 e9 8e fe ff ff 48 89 df e8 26 30 c7 f9 eb 8a cc cc cc cc e9 07 00 00 00 0f 00 2d 14 4b 5c 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 04 4b 5c 00 f4 c3 cc cc 55 53 e8 c9
RSP: 0018:ffffc90000d3fd18 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff8880a95f0340 RSI: ffffffff87ec78c8 RDI: ffffffff87ec789e
RBP: ffff88821af4d864 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88821af4d864
R13: 1ffff920001a7fad R14: ffff88821af4d865 R15: 0000000000000001
 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline]
 acpi_safe_halt+0x8d/0x110 drivers/acpi/processor_idle.c:111
 acpi_idle_do_entry+0x15c/0x1b0 drivers/acpi/processor_idle.c:525
 acpi_idle_enter+0x3f9/0xab0 drivers/acpi/processor_idle.c:651
 cpuidle_enter_state+0xff/0x960 drivers/cpuidle/cpuidle.c:235
 cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:346
 call_cpuidle kernel/sched/idle.c:126 [inline]
 cpuidle_idle_call kernel/sched/idle.c:214 [inline]
 do_idle+0x431/0x6d0 kernel/sched/idle.c:276
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:372
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243


Memory state around the buggy address:
 ffffc900016d7480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc900016d7500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc900016d7580: 00 00 00 00 f1 f1 f1 f1 00 00 00 00 f3 f3 f3 f3
                                                                ^
 ffffc900016d7600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc900016d7680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================