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SubjectKASAN: slab-out-of-bounds Read in tick_sched_handle

syzbot found the following crash on:

HEAD commit: c151acc6e9ff l2tp: Add protocol field decompression
git tree: net-next
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:
C reproducer:

IMPORTANT: if you fix the bug, please add the following tag to the commit:

IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
kasan: CONFIG_KASAN_INLINE enabled
BUG: KASAN: slab-out-of-bounds in tick_sched_handle+0x16c/0x180
kasan: GPF could be caused by NULL-ptr deref or user memory access
Read of size 8 at addr ffff8881d8b67b70 by task syz-executor132/5936
general protection fault: 0000 [#1] PREEMPT SMP KASAN

CPU: 0 PID: 5936 Comm: syz-executor132 Not tainted 4.20.0-rc6+ #347
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.20.0-rc6+ #347
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
RIP: 0010:lookup_object lib/debugobjects.c:156 [inline]
RIP: 0010:debug_object_deactivate+0x191/0x450 lib/debugobjects.c:542
Code: 02 00 00 48 8b 1b 41 bf 01 00 00 00 48 85 db 74 46 48 b8 00 00 00 00
00 fc ff df 48 8d 7b 18 41 83 c7 01 48 89 fe 48 c1 ee 03 <80> 3c 06 00 0f
85 04 02 00 00 48 3b 53 18 0f 84 53 01 00 00 48 89
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
RSP: 0018:ffff8881daf078b0 EFLAGS: 00010807
RAX: dffffc0000000000 RBX: da3ef506c4b2a03d RCX: ffffffff83939c1a
RDX: ffff8881bb4ed108 RSI: 1b47dea0d896540a RDI: da3ef506c4b2a055
RBP: ffff8881daf07968 R08: ffffed103b5e0f03 R09: ffffed103b5e0f02
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
R10: ffffed103b5e0f02 R11: 0000000000000003 R12: 1ffff1103b5e0f18
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
R13: ffffffff8b23e7a8 R14: ffffffff895a5980 R15: 0000000000000003
FS: 0000000000000000(0000) GS:ffff8881daf00000(0000) knlGS:0000000000000000
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
tick_sched_handle+0x16c/0x180 kernel/time/tick-sched.c:164
CR2: 0000000000619570 CR3: 00000001c3506000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1460
Call Trace:
debug_timer_deactivate kernel/time/timer.c:714 [inline]
debug_deactivate kernel/time/timer.c:770 [inline]
detach_timer kernel/time/timer.c:815 [inline]
expire_timers kernel/time/timer.c:1353 [inline]
__run_timers+0x56f/0xc70 kernel/time/timer.c:1682
hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1034 [inline]
smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1059
run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1695
__do_softirq+0x308/0xb7e kernel/softirq.c:292
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807

Allocated by task 5092:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x17f/0x1c0 kernel/softirq.c:413
getname_flags+0xd0/0x590 fs/namei.c:140
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
user_path_at_empty+0x2d/0x50 fs/namei.c:2608
user_path_at include/linux/namei.h:57 [inline]
do_faccessat+0x254/0x800 fs/open.c:378
__do_sys_access fs/open.c:430 [inline]
__se_sys_access fs/open.c:428 [inline]
__x64_sys_access+0x59/0x80 fs/open.c:428
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290

Freed by task 5092:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x83/0x290 mm/slab.c:3760
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
putname+0xf2/0x130 fs/namei.c:261
filename_lookup+0x39a/0x520 fs/namei.c:2357
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:58
user_path_at_empty+0x40/0x50 fs/namei.c:2608
Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 d3 ac e5 f9 48 8b 45 d8 e9 ca
fe ff ff 48 89 df e8 c2 ac e5 f9 eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84
00 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90
user_path_at include/linux/namei.h:57 [inline]
do_faccessat+0x254/0x800 fs/open.c:378
RSP: 0018:ffff8881d9b27cb8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
__do_sys_access fs/open.c:430 [inline]
__se_sys_access fs/open.c:428 [inline]
__x64_sys_access+0x59/0x80 fs/open.c:428
RAX: dffffc0000000000 RBX: 1ffff1103b364f9b RCX: 0000000000000000
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
RDX: 1ffffffff12a4021 RSI: 0000000000000001 RDI: ffffffff89520108
RBP: ffff8881d9b27cb8 R08: ffff8881d9b14340 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881d9b27d78

R13: ffffffff8a166760 R14: 0000000000000000 R15: 0000000000000001
The buggy address belongs to the object at ffff8881d8b66100
which belongs to the cache names_cache of size 4096
arch_safe_halt arch/x86/include/asm/paravirt.h:151 [inline]
default_idle+0xbf/0x490 arch/x86/kernel/process.c:561
The buggy address is located 2672 bytes to the right of
4096-byte region [ffff8881d8b66100, ffff8881d8b67100)
The buggy address belongs to the page:
page:ffffea000762d980 count:1 mapcount:0 mapping:ffff8881da980e00 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea0007628f08 ffffea000762dc88 ffff8881da980e00
raw: 0000000000000000 ffff8881d8b66100 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881d8b67a00: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc
ffff8881d8b67a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:552
> ffff8881d8b67b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
ffff8881d8b67b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881d8b67c00: fc fc fc fc fc 00 00 00 00 00 00 00 00 00 00 00

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