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BUG: KASAN: slab-out-of-bounds in __list_del_entry_valid+0x10b/0x150 lib/list_debug.c:51
Read of size 8 at addr ffff88006975fa80 by task syz-executor4/13081

CPU: 3 PID: 13081 Comm: syz-executor4 Not tainted 4.13.0-next-20170904+ #14
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 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+0x24e/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 __list_del_entry_valid+0x10b/0x150 lib/list_debug.c:51
 __list_del_entry include/linux/list.h:116 [inline]
 list_del include/linux/list.h:124 [inline]
 __remove_wait_queue include/linux/wait.h:182 [inline]
 userfaultfd_event_wait_completion+0x519/0x910 fs/userfaultfd.c:591
 dup_fctx fs/userfaultfd.c:687 [inline]
 dup_userfaultfd_complete+0x2de/0x480 fs/userfaultfd.c:695
 dup_mmap kernel/fork.c:726 [inline]
 dup_mm kernel/fork.c:1179 [inline]
 copy_mm+0xe9b/0x1310 kernel/fork.c:1233
 copy_process.part.36+0x1eae/0x4af0 kernel/fork.c:1735
 copy_process kernel/fork.c:1548 [inline]
 _do_fork+0x1ef/0xfe0 kernel/fork.c:2027
 SYSC_clone kernel/fork.c:2137 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2131
 do_syscall_64+0x26c/0x8c0 arch/x86/entry/common.c:287
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x447299
RSP: 002b:00007f6f41b81c08 EFLAGS: 00000282 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000447299
RDX: 0000000020d6f000 RSI: 0000000020d42fff RDI: 0000000000000000
RBP: 0000000000708160 R08: 0000000020497000 R09: 0000000000000000
R10: 0000000020a6bffc R11: 0000000000000282 R12: 00000000ffffffff
R13: 0000000000000450 R14: 00000000006e3510 R15: 0000000020d42fff

Allocated by task 13101:
 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]
 perf_event_mmap_event kernel/events/core.c:6943 [inline]
 perf_event_mmap+0x4b2/0x1170 kernel/events/core.c:7137
 mmap_region+0x3e5/0x15a0 mm/mmap.c:1721
 do_mmap+0x6a1/0xd50 mm/mmap.c:1468
 do_mmap_pgoff include/linux/mm.h:2151 [inline]
 vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
 vm_mmap+0x6a/0x90 mm/util.c:352
 elf_map+0x1c7/0x230 fs/binfmt_elf.c:373
 load_elf_binary+0xc17/0x4970 fs/binfmt_elf.c:989
 search_binary_handler+0x142/0x6b0 fs/exec.c:1652
 exec_binprm fs/exec.c:1694 [inline]
 do_execveat_common.isra.33+0x1746/0x22e0 fs/exec.c:1816
 do_execve+0x31/0x40 fs/exec.c:1860
 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

Freed by task 13101:
 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
 perf_event_mmap_event kernel/events/core.c:7023 [inline]
 perf_event_mmap+0xa0d/0x1170 kernel/events/core.c:7137
 mmap_region+0x3e5/0x15a0 mm/mmap.c:1721
 do_mmap+0x6a1/0xd50 mm/mmap.c:1468
 do_mmap_pgoff include/linux/mm.h:2151 [inline]
 vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
 vm_mmap+0x6a/0x90 mm/util.c:352
 elf_map+0x1c7/0x230 fs/binfmt_elf.c:373
 load_elf_binary+0xc17/0x4970 fs/binfmt_elf.c:989
 search_binary_handler+0x142/0x6b0 fs/exec.c:1652
 exec_binprm fs/exec.c:1694 [inline]
 do_execveat_common.isra.33+0x1746/0x22e0 fs/exec.c:1816
 do_execve+0x31/0x40 fs/exec.c:1860
 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

The buggy address belongs to the object at ffff88006975e180
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 2304 bytes to the right of
 4096-byte region [ffff88006975e180, ffff88006975f180)
The buggy address belongs to the page:
page:ffffea0001a5d780 count:1 mapcount:0 mapping:ffff88006975e180 index:0x0 compound_mapcount: 0
flags: 0x500000000008100(slab|head)
raw: 0500000000008100 ffff88006975e180 0000000000000000 0000000100000001
raw: ffffea0001a5d720 ffffea000168d020 ffff88003e800dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88006975f980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88006975fa00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88006975fa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff88006975fb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88006975fb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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