BUG: KASAN: use-after-free in __lock_acquire+0x407b/0x4620 kernel/locking/lockdep.c:3376
Read of size 8 at addr ffff8801c70f6068 by task syz-executor0/5591

CPU: 1 PID: 5591 Comm: syz-executor0 Not tainted 4.14.0-rc2-next-20170927+ #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 __lock_acquire+0x407b/0x4620 kernel/locking/lockdep.c:3376
 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002
 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
 _raw_spin_lock_irq+0x5e/0x80 kernel/locking/spinlock.c:167
 exit_pi_state_list+0x369/0x7a0 kernel/futex.c:914
 mm_release+0x46d/0x590 kernel/fork.c:1126
 exit_mm kernel/exit.c:499 [inline]
 do_exit+0x481/0x1b00 kernel/exit.c:852
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73f/0x16d0 kernel/signal.c:2334
 do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath+0x42f/0x510 arch/x86/entry/common.c:266
 entry_SYSCALL_64_fastpath+0xbc/0xbe
RIP: 0033:0x4520a9
RSP: 002b:00007f237f21ecf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 0000000000718028 RCX: 00000000004520a9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000718028
RBP: 0000000000718000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffff69fceef R14: 00007f237f21f9c0 R15: 0000000000000000

Allocated by task 5614:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3627
 kmalloc include/linux/slab.h:493 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 refill_pi_state_cache.part.6+0xa5/0x2f0 kernel/futex.c:790
 refill_pi_state_cache kernel/futex.c:1810 [inline]
 futex_requeue+0x1887/0x2370 kernel/futex.c:1877
 do_futex+0x7f5/0x20d0 kernel/futex.c:3488
 SYSC_futex kernel/futex.c:3526 [inline]
 SyS_futex+0x260/0x390 kernel/futex.c:3494
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 5603:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xca/0x250 mm/slab.c:3820
 put_pi_state+0x3f4/0x560 kernel/futex.c:852
 unqueue_me_pi+0x4a/0xc0 kernel/futex.c:2266
 futex_wait_requeue_pi.constprop.19+0xc7f/0x1300 kernel/futex.c:3185
 do_futex+0x825/0x20d0 kernel/futex.c:3485
 SYSC_futex kernel/futex.c:3526 [inline]
 SyS_futex+0x260/0x390 kernel/futex.c:3494
 entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff8801c70f6040
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 40 bytes inside of
 256-byte region [ffff8801c70f6040, ffff8801c70f6140)
The buggy address belongs to the page:
page:ffffea00071c3d80 count:1 mapcount:0 mapping:ffff8801c70f6040 index:0x0
flags: 0x200000000000100(slab)
raw: 0200000000000100 ffff8801c70f6040 0000000000000000 000000010000000c
raw: ffffea00071d4c60 ffffea00071ca720 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c70f5f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c70f5f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c70f6000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801c70f6080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c70f6100: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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