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BUG: KASAN: use-after-free in filemap_fault+0x25f5/0x2a00 mm/filemap.c:2559
Read of size 8 at addr ffff8880a3c03880 by task syz-executor0/18166

CPU: 1 PID: 18166 Comm: syz-executor0 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
 ext4_filemap_fault+0x83/0xaf fs/ext4/inode.c:6327
 __do_fault+0x176/0x7b0 mm/memory.c:3013
 do_read_fault mm/memory.c:3424 [inline]
 do_fault mm/memory.c:3550 [inline]
 handle_pte_fault mm/memory.c:3781 [inline]
 __handle_mm_fault+0x370a/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: 0010:do_strncpy_from_user lib/strncpy_from_user.c:45 [inline]
RIP: 0010:strncpy_from_user+0x21f/0x440 lib/strncpy_from_user.c:118
Code: bf 07 00 00 00 49 83 c4 08 48 89 de e8 1a f3 dd fd 48 83 fb 07 0f 86 75 01 00 00 e8 6b f1 dd fd 45 31 f6 48 8b 85 70 ff ff ff <4e> 8b 3c 20 31 ff 44 89 f6 e8 d3 f2 dd fd 45 85 f6 0f 84 5e ff ff
RSP: 0018:ffff8880467ffc40 EFLAGS: 00010246
RAX: 0000000020000780 RBX: 0000000000000fe0 RCX: ffffc90005fd2000
RDX: 0000000000000316 RSI: ffffffff83a40f95 RDI: 0000000000000007
RBP: ffff8880467ffcf0 R08: ffff88803844a680 R09: ffff88821bc49080
R10: 000000000000001c R11: ffff888033c6537f R12: 0000000000000000
R13: ffff888033c643a0 R14: 0000000000000000 R15: 8080808080808080
 getname_flags fs/namei.c:151 [inline]
 getname_flags+0x11b/0x5b0 fs/namei.c:129
 getname+0x1a/0x20 fs/namei.c:211
 do_sys_open+0x3a5/0x7c0 fs/open.c:1057
 __do_sys_open fs/open.c:1081 [inline]
 __se_sys_open fs/open.c:1076 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1076
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ec9
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f52141a4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457ec9
RDX: 0000000000000000 RSI: 000000000014103e RDI: 0000000020000780
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f52141a56d4
R13: 00000000004f471f R14: 00000000004d6d30 R15: 00000000ffffffff

Allocated by task 18166:
 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 18168:
 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 ffff8880a3c03840
 which belongs to the cache vm_area_struct(17:syz0) of size 200
The buggy address is located 64 bytes inside of
 200-byte region [ffff8880a3c03840, ffff8880a3c03908)
The buggy address belongs to the page:
page:ffffea00028f00c0 count:1 mapcount:0 mapping:ffff88808d77c240 index:0xffff8880a3c03000
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002793b88 ffffea00023456c8 ffff88808d77c240
raw: ffff8880a3c03000 ffff8880a3c03000 0000000100000009 ffff88805c244a80
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88805c244a80

Memory state around the buggy address:
 ffff8880a3c03780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a3c03800: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8880a3c03880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880a3c03900: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb
 ffff8880a3c03980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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