==================================================================
BUG: KASAN: use-after-free in ext4_data_block_valid+0x2d5/0x330 fs/ext4/block_validity.c:211
Read of size 8 at addr ffff8801c9f72750 by task syz-executor0/5693

CPU: 0 PID: 5693 Comm: syz-executor0 Not tainted 4.19.0-next-20181102+ #104
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+0x244/0x39d lib/dump_stack.c:113
 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ext4_data_block_valid+0x2d5/0x330 fs/ext4/block_validity.c:211
 __check_block_validity.constprop.79+0xc1/0x210 fs/ext4/inode.c:402
 ext4_map_blocks+0x1021/0x1b50 fs/ext4/inode.c:592
 ext4_getblk+0x4f2/0x630 fs/ext4/inode.c:966
 ext4_bread_batch+0x7f/0x440 fs/ext4/inode.c:1036
 ext4_find_entry+0xd49/0x1b70 fs/ext4/namei.c:1425
 ext4_lookup+0x15b/0x700 fs/ext4/namei.c:1557
 __lookup_slow+0x2b5/0x540 fs/namei.c:1671
 lookup_slow+0x57/0x80 fs/namei.c:1688
 mountpoint_last fs/namei.c:2665 [inline]
 path_mountpoint+0x6e4/0x2180 fs/namei.c:2695
 filename_mountpoint+0x245/0x460 fs/namei.c:2717
 user_path_mountpoint_at+0x37/0x40 fs/namei.c:2747
 ksys_umount+0x1c9/0x1230 fs/namespace.c:1620
 __do_sys_umount fs/namespace.c:1646 [inline]
 __se_sys_umount fs/namespace.c:1644 [inline]
 __x64_sys_umount+0x54/0x80 fs/namespace.c:1644
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459fb7
Code: 44 00 00 b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 9d 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 7d 89 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc4350f0f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 00000000000469f8 RCX: 0000000000459fb7
RDX: 000000000000000c RSI: 0000000000000002 RDI: 00007ffc43510230
RBP: 000000000000016b R08: 0000000000000001 R09: 00000000026f9940
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc43510230
R13: 00000000000469db R14: 0000000000000000 R15: 0000000000000000

Allocated by task 1:
 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
 add_system_zone+0x2e5/0x5f0 fs/ext4/block_validity.c:85
 ext4_setup_system_zone+0x208/0x520 fs/ext4/block_validity.c:169
 ext4_fill_super+0x8180/0xdbb0 fs/ext4/super.c:4386
 mount_bdev+0x314/0x3e0 fs/super.c:1356
 ext4_mount+0x3c/0x50 fs/ext4/super.c:5895
 legacy_get_tree+0x12f/0x260 fs/fs_context.c:714
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1795
 do_new_mount fs/namespace.c:2704 [inline]
 do_mount+0x82a/0x1ff0 fs/namespace.c:3030
 ksys_mount+0x12d/0x140 fs/namespace.c:3246
 do_mount_root+0x35/0x1d3 init/do_mounts.c:388
 mount_block_root+0x39c/0x6ed init/do_mounts.c:417
 mount_root+0x358/0x39f init/do_mounts.c:562
 prepare_namespace+0x26c/0x2ab init/do_mounts.c:621
 kernel_init_freeable+0x69b/0x6b9 init/main.c:1170
 kernel_init+0x11/0x1ae init/main.c:1071
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Freed by task 8098:
 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
 ext4_release_system_zone+0x7c/0x110 fs/ext4/block_validity.c:187
 ext4_setup_system_zone+0x3ef/0x520 fs/ext4/block_validity.c:151
 ext4_remount+0x16fc/0x2980 fs/ext4/super.c:5340
 legacy_reconfigure+0x14c/0x1c0 fs/fs_context.c:738
 reconfigure_super+0x4c0/0xbb0 fs/super.c:982
 do_remount fs/namespace.c:2422 [inline]
 do_mount+0x1ab4/0x1ff0 fs/namespace.c:3021
 ksys_mount+0x12d/0x140 fs/namespace.c:3246
 __do_sys_mount fs/namespace.c:3260 [inline]
 __se_sys_mount fs/namespace.c:3257 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3257
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801c9f72738
 which belongs to the cache ext4_system_zone of size 40
The buggy address is located 24 bytes inside of
 40-byte region [ffff8801c9f72738, ffff8801c9f72760)
The buggy address belongs to the page:
page:ffffea000727dc80 count:1 mapcount:0 mapping:ffff8801d451dc00 index:0xffff8801c9f72fb9
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffff8801d4524f38 ffff8801d4524f38 ffff8801d451dc00
raw: ffff8801c9f72fb9 ffff8801c9f72000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c9f72600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c9f72680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c9f72700: fc fc fc fc fc fc fc fb fb fb fb fb fc fc fb fb
                                                 ^
 ffff8801c9f72780: fb fb fb fc fc fb fb fb fb fb fc fc fb fb fb fb
 ffff8801c9f72800: fb fc fc fb fb fb fb fb fc fc fb fb fb fb fb fc
==================================================================
EXT4-fs (sda1): re-mounted. Opts: noblock_validity,,errors=continue