------------[ cut here ]------------
WARNING: CPU: 0 PID: 5336 at fs/buffer.c:1183 mark_buffer_dirty+0x2a9/0x410 fs/buffer.c:1183
Modules linked in:
CPU: 0 UID: 0 PID: 5336 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:mark_buffer_dirty+0x2a9/0x410 fs/buffer.c:1183
Code: 4c 89 f7 e8 69 08 dd ff 49 8b 3e be 40 00 00 00 5b 41 5c 41 5e 41 5f 5d e9 14 ea fb ff e8 ff bc 75 ff eb 8c e8 f8 bc 75 ff 90 <0f> 0b 90 e9 95 fd ff ff e8 ea bc 75 ff 90 0f 0b 90 e9 bf fd ff ff
RSP: 0018:ffffc9000d4764c8 EFLAGS: 00010293
RAX: ffffffff824a5658 RBX: ffff888042ed0828 RCX: ffff888000258000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffff888035e62001 R08: ffff888042ed082f R09: 1ffff110085da105
R10: dffffc0000000000 R11: ffffed10085da106 R12: ffff88804c17da00
R13: ffff888042ed0488 R14: ffff888042ed0828 R15: 000000000000000a
FS:  00007f94add926c0(0000) GS:ffff88808d72f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcef71af04 CR3: 0000000052510000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 bfs_move_block fs/bfs/file.c:44 [inline]
 bfs_move_blocks fs/bfs/file.c:57 [inline]
 bfs_get_block+0x5da/0xae0 fs/bfs/file.c:126
 __block_write_begin_int+0x6b5/0x1900 fs/buffer.c:2145
 block_write_begin+0x8a/0x120 fs/buffer.c:2256
 bfs_write_begin+0x35/0xd0 fs/bfs/file.c:180
 generic_perform_write+0x2c5/0x900 mm/filemap.c:4254
 generic_file_write_iter+0x117/0x550 mm/filemap.c:4397
 __kernel_write_iter+0x428/0x910 fs/read_write.c:619
 __kernel_write+0xef/0x150 fs/read_write.c:639
 __dump_emit+0x206/0x310 fs/coredump.c:1220
 elf_core_dump+0x2d05/0x3960 fs/binfmt_elf.c:2090
 coredump_write+0x116c/0x1900 fs/coredump.c:1049
 vfs_coredump+0x1db5/0x2a60 fs/coredump.c:1170
 get_signal+0x1108/0x1340 kernel/signal.c:3019
 arch_do_signal_or_restart+0xa0/0x790 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x72/0x130 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 ret_from_fork+0x53f/0x870 arch/x86/kernel/process.c:167
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>