==================================================================
BUG: KASAN: use-after-free in ext4_data_block_valid+0x2d5/0x330 fs/ext4/block_validity.c:211
Read of size 8 at addr ffff8801c9f6f750 by task syz-executor5/5686

CPU: 1 PID: 5686 Comm: syz-executor5 Not tainted 4.19.0-rc7-next-20181012+ #93
EXT4-fs (sda1): re-mounted. Opts: noblock_validity,grpid,usrquota,errors=continue,jqfmt=vfsv0,,errors=continue
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+0x244/0x3ab 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.78+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+0x95/0x2b0 fs/ext4/inode.c:1016
 __ext4_read_dirblock+0x37/0x940 fs/ext4/namei.c:101
 htree_dirblock_to_tree+0x13a/0xae0 fs/ext4/namei.c:978
 ext4_htree_fill_tree+0x40c/0xd60 fs/ext4/namei.c:1097
 ext4_dx_readdir fs/ext4/dir.c:576 [inline]
 ext4_readdir+0x1ca1/0x3c30 fs/ext4/dir.c:121
 iterate_dir+0x48c/0x5d0 fs/readdir.c:51
 __do_sys_getdents fs/readdir.c:231 [inline]
 __se_sys_getdents fs/readdir.c:212 [inline]
 __x64_sys_getdents+0x29f/0x510 fs/readdir.c:212
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45594b
Code: 02 74 b6 31 f6 eb b9 0f 1f 84 00 00 00 00 00 41 57 41 56 48 63 ff 41 55 41 54 b8 4e 00 00 00 55 53 48 89 f3 48 83 ec 08 0f 05 <48> 3d 00 f0 ff ff 77 55 4c 8d 24 06 49 89 c5 4c 39 e6 73 33 90 0f
RSP: 002b:00007ffdb760c810 EFLAGS: 00000202 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 000000000250f970 RCX: 000000000045594b
RDX: 0000000000008000 RSI: 000000000250f970 RDI: 0000000000000003
RBP: 000000000250f970 R08: 0000000000000001 R09: 000000000250e940
R10: 0000000000000000 R11: 0000000000000202 R12: ffffffffffffffd4
R13: 0000000000000016 R14: 0000000000000000 R15: 0000000000000005

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+0x131/0x460 fs/fs_context.c:718
 vfs_get_tree+0x1cb/0x5c0 fs/super.c:1795
 do_new_mount fs/namespace.c:2648 [inline]
 do_mount+0x70c/0x1d90 fs/namespace.c:2974
 ksys_mount+0x12d/0x140 fs/namespace.c:3190
 do_mount_root+0x35/0x1d3 init/do_mounts.c:388
 mount_block_root+0x39c/0x6ed init/do_mounts.c:417
 mount_root+0x2d3/0x31a init/do_mounts.c:562
 prepare_namespace+0x26c/0x2ab init/do_mounts.c:621
 kernel_init_freeable+0x69b/0x6b9 init/main.c:1167
 kernel_init+0x11/0x1ae init/main.c:1068
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Freed by task 13745:
 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:754
 reconfigure_super+0x4c0/0xbb0 fs/super.c:982
 do_remount fs/namespace.c:2419 [inline]
 do_mount+0x18b9/0x1d90 fs/namespace.c:2965
 ksys_mount+0x12d/0x140 fs/namespace.c:3190
 __do_sys_mount fs/namespace.c:3204 [inline]
 __se_sys_mount fs/namespace.c:3201 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3201
 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 ffff8801c9f6f738
 which belongs to the cache ext4_system_zone of size 40
The buggy address is located 24 bytes inside of
 40-byte region [ffff8801c9f6f738, ffff8801c9f6f760)
The buggy address belongs to the page:
page:ffffea000727dbc0 count:1 mapcount:0 mapping:ffff8801d4b2ed80 index:0xffff8801c9f6ffb9
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffff8801d4b28038 ffff8801d4b28038 ffff8801d4b2ed80
raw: ffff8801c9f6ffb9 ffff8801c9f6f000 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c9f6f600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801c9f6f680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c9f6f700: fc fc fc fc fc fc fc fb fb fb fb fb fc fc fb fb
                                                 ^
 ffff8801c9f6f780: fb fb fb fc fc fb fb fb fb fb fc fc fb fb fb fb
 ffff8801c9f6f800: fb fc fc fb fb fb fb fb fc fc fb fb fb fb fb fc
==================================================================
kobject: 'loop2' (0000000001165c71): kobject_uevent_env
kobject: 'loop2' (0000000001165c71): fill_kobj_path: path = '/devices/virtual/block/loop2'