==================================================================
BUG: KASAN: null-ptr-deref in write_dirty_buffer+0x37/0x190
Write of size 8 at addr 0000000000000000 by task syz-executor/17912

CPU: 1 UID: 0 PID: 17912 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 kasan_report+0x117/0x150
 kasan_check_range+0x264/0x2c0
 write_dirty_buffer+0x37/0x190
 mmb_sync+0x74c/0xed0
 udf_evict_inode+0x22f/0x4c0
 evict+0x61e/0xb10
 evict_inodes+0x75a/0x7f0
 generic_shutdown_super+0xaa/0x2d0
 kill_block_super+0x44/0x90
 deactivate_locked_super+0xbc/0x130
 cleanup_mnt+0x437/0x4d0
 task_work_run+0x1d9/0x270
 exit_to_user_mode_loop+0xf3/0x4d0
 do_syscall_64+0x33e/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f45ae79e017
Code: a2 c7 05 dc 06 25 00 00 00 00 00 eb 96 e8 e1 12 00 00 90 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007fff5aea6fc8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f45ae832120 RCX: 00007f45ae79e017
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007fff5aea7080
RBP: 00007fff5aea7080 R08: 00007fff5aea8080 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff5aea8110
R13: 00007f45ae832120 R14: 00000000000952a3 R15: 00007fff5aea8150
 </TASK>
==================================================================
