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BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x2de/0x320 fs/ext4/dir.c:69
Read of size 2 at addr ffff88017a871002 by task syz-executor2/11782

CPU: 0 PID: 11782 Comm: syz-executor2 Not tainted 4.16.0-rc7+ #9
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:431
 __ext4_check_dir_entry+0x2de/0x320 fs/ext4/dir.c:69
 ext4_readdir+0xd00/0x3600 fs/ext4/dir.c:237
 iterate_dir+0x1ca/0x530 fs/readdir.c:51
 SYSC_getdents64 fs/readdir.c:314 [inline]
 SyS_getdents64+0x221/0x420 fs/readdir.c:295
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x454e79
RSP: 002b:00007fe971106c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007fe9711076d4 RCX: 0000000000454e79
RDX: 00000000200015fc RSI: 0000000020001540 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000000a9 R14: 00000000006f3078 R15: 0000000000000000

Allocated by task 2258:
 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:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3542
 mempool_alloc_slab+0x44/0x60 mm/mempool.c:450
 mempool_alloc+0x16a/0x4b0 mm/mempool.c:330
 bio_alloc_bioset+0x3cd/0x760 block/bio.c:486
 bio_alloc include/linux/bio.h:428 [inline]
 submit_bh_wbc+0x105/0x710 fs/buffer.c:3073
 submit_bh+0x28/0x30 fs/buffer.c:3105
 jbd2_journal_commit_transaction+0x221d/0x7e20 fs/jbd2/commit.c:710
 kjournald2+0x244/0x9f0 fs/jbd2/journal.c:229
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

Freed by task 0:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3486 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3744
 mempool_free_slab+0x1d/0x30 mm/mempool.c:457
 mempool_free+0xd8/0x350 mm/mempool.c:439
 bio_free+0x12b/0x1a0 block/bio.c:265
 bio_put+0x14f/0x180 block/bio.c:558
 end_bio_bh_io_sync+0xcd/0x110 fs/buffer.c:2993
 bio_endio+0x447/0x950 block/bio.c:1775
 req_bio_endio block/blk-core.c:208 [inline]
 blk_update_request+0x265/0xda0 block/blk-core.c:2990
 scsi_end_request+0xc8/0x820 drivers/scsi/scsi_lib.c:660
 scsi_io_completion+0x8ab/0x16b0 drivers/scsi/scsi_lib.c:868
 scsi_finish_command+0x5f6/0x890 drivers/scsi/scsi.c:248
 scsi_softirq_done+0x3ab/0x480 drivers/scsi/scsi_lib.c:1653
 __blk_mq_complete_request+0x564/0x990 block/blk-mq.c:559
 blk_mq_complete_request+0x1f6/0x320 block/blk-mq.c:644
 scsi_mq_done+0xd6/0x3c0 drivers/scsi/scsi_lib.c:1964
 virtscsi_complete_cmd+0x489/0x6f0 drivers/scsi/virtio_scsi.c:207
 virtscsi_vq_done+0xc1/0x150 drivers/scsi/virtio_scsi.c:223
 virtscsi_req_done+0xa7/0xd0 drivers/scsi/virtio_scsi.c:238
 vring_interrupt+0x109/0x150 drivers/virtio/virtio_ring.c:951
 __handle_irq_event_percpu+0x1ad/0x9d0 kernel/irq/handle.c:147
 handle_irq_event_percpu+0x98/0x1b0 kernel/irq/handle.c:187
 handle_irq_event+0xa7/0x140 kernel/irq/handle.c:204
 handle_edge_irq+0x1d5/0x7c0 kernel/irq/chip.c:793
 generic_handle_irq_desc include/linux/irqdesc.h:159 [inline]
 handle_irq+0x17a/0x300 arch/x86/kernel/irq_64.c:77
 do_IRQ+0x78/0x190 arch/x86/kernel/irq.c:238

The buggy address belongs to the object at ffff88017a871000
 which belongs to the cache bio-0 of size 200
The buggy address is located 2 bytes inside of
 200-byte region [ffff88017a871000, ffff88017a8710c8)
The buggy address belongs to the page:
page:ffffea0005ea1c40 count:1 mapcount:0 mapping:ffff88017a871000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff88017a871000 0000000000000000 000000010000000c
raw: ffffea0006b126a0 ffff8801d7e70348 ffff8801d7e713c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88017a870f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88017a870f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88017a871000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88017a871080: fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc
 ffff88017a871100: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
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