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BUG: KASAN: use-after-free in filemap_fault+0x25f5/0x2a00 mm/filemap.c:2559
Read of size 8 at addr ffff88808e961988 by task syz-executor2/27272

CPU: 0 PID: 27272 Comm: syz-executor2 Not tainted 4.20.0-next-20190103 #5
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
 filemap_fault+0x25f5/0x2a00 mm/filemap.c:2559
 __do_fault+0x176/0x7b0 mm/memory.c:3013
 do_shared_fault mm/memory.c:3479 [inline]
 do_fault mm/memory.c:3554 [inline]
 handle_pte_fault mm/memory.c:3781 [inline]
 __handle_mm_fault+0x3500/0x55a0 mm/memory.c:3905
 handle_mm_fault+0x4ec/0xc80 mm/memory.c:3942
 do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
 __do_page_fault+0x5da/0xd60 arch/x86/mm/fault.c:1541
 do_page_fault+0xe6/0x7d8 arch/x86/mm/fault.c:1572
 page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
RIP: 0033:0x401c1c
Code: ff 01 64 48 8b 3c 25 00 00 00 00 48 81 c7 08 ff ff ff e8 87 e5 01 00 85 c0 75 13 48 63 44 24 04 48 8b 54 24 18 48 8b 4c 24 08 <48> 89 0c c2 64 f0 83 2c 25 d0 ff ff ff 01 64 f0 83 04 25 d0 ff ff
RSP: 002b:00007f58ab4b6030 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000860000109120
RDX: 0000000020480800 RSI: 0000000000000000 RDI: 00007f58ab4b8608
RBP: 0000000020480800 R08: 0000000000000090 R09: 000000000000000b
R10: 00000000000000b3 R11: 0000000000000206 R12: 000000002aaaaaab
R13: 000000002047d000 R14: 00000000004db608 R15: 00000000ffffffff

Allocated by task 27267:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 kasan_kmalloc mm/kasan/common.c:482 [inline]
 kasan_kmalloc+0xcf/0xe0 mm/kasan/common.c:455
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:397
 kmem_cache_alloc+0x12d/0x710 mm/slab.c:3541
 vm_area_alloc+0x7a/0x1d0 kernel/fork.c:331
 mmap_region+0x93b/0x1ca0 mm/mmap.c:1756
 do_mmap+0xa09/0x1220 mm/mmap.c:1559
 do_mmap_pgoff include/linux/mm.h:2421 [inline]
 vm_mmap_pgoff+0x20b/0x2b0 mm/util.c:350
 ksys_mmap_pgoff+0x4f8/0x650 mm/mmap.c:1609
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 27267:
 save_stack+0x45/0xd0 mm/kasan/common.c:73
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:444
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
 __cache_free mm/slab.c:3485 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3747
 vm_area_free+0x1d/0x30 kernel/fork.c:350
 remove_vma+0x142/0x180 mm/mmap.c:185
 remove_vma_list mm/mmap.c:2585 [inline]
 __do_munmap+0x72e/0xef0 mm/mmap.c:2828
 do_munmap mm/mmap.c:2836 [inline]
 mmap_region+0x698/0x1ca0 mm/mmap.c:1729
 do_mmap+0xa09/0x1220 mm/mmap.c:1559
 do_mmap_pgoff include/linux/mm.h:2421 [inline]
 vm_mmap_pgoff+0x20b/0x2b0 mm/util.c:350
 ksys_mmap_pgoff+0x4f8/0x650 mm/mmap.c:1609
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808e961948
 which belongs to the cache vm_area_struct(49:syz2) of size 200
The buggy address is located 64 bytes inside of
 200-byte region [ffff88808e961948, ffff88808e961a10)
The buggy address belongs to the page:
page:ffffea00023a5840 count:1 mapcount:0 mapping:ffff88808ae82680 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000243fe88 ffffea00016820c8 ffff88808ae82680
raw: 0000000000000000 ffff88808e961000 000000010000000f ffff88805830cc40
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88805830cc40

Memory state around the buggy address:
 ffff88808e961880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808e961900: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb
>ffff88808e961980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88808e961a00: fb fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb
 ffff88808e961a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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