============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5332 is trying to acquire lock:
ffff888034170528 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_free_blocks fs/udf/balloc.c:375 [inline]
ffff888034170528 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_free_blocks+0xaaf/0x1940 fs/udf/balloc.c:677

but task is already holding lock:
ffff888034170528 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_prealloc_blocks fs/udf/balloc.c:516 [inline]
ffff888034170528 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x8f6/0x1130 fs/udf/balloc.c:701

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&sbi->s_alloc_mutex);
  lock(&sbi->s_alloc_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by syz.0.0/5332:
 #0: ffff88801f582420 (sb_writers#12){.+.+}-{0:0}, at: do_coredump fs/coredump.c:1126 [inline]
 #0: ffff88801f582420 (sb_writers#12){.+.+}-{0:0}, at: vfs_coredump+0x369e/0x4270 fs/coredump.c:1200
 #1: ffff888047d85be0 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
 #1: ffff888047d85be0 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: udf_file_write_iter+0x6f/0x6b0 fs/udf/file.c:95
 #2: ffff888047d85a10 (&ei->i_data_sem#2){++++}-{4:4}, at: udf_map_block+0x2a4/0x4330 fs/udf/inode.c:446
 #3: ffff888034170528 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_prealloc_blocks fs/udf/balloc.c:516 [inline]
 #3: ffff888034170528 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x8f6/0x1130 fs/udf/balloc.c:701

stack backtrace:
CPU: 0 UID: 0 PID: 5332 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 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x253f/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:614 [inline]
 __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776
 udf_table_free_blocks fs/udf/balloc.c:375 [inline]
 udf_free_blocks+0xaaf/0x1940 fs/udf/balloc.c:677
 udf_delete_aext+0x4fb/0xbd0 fs/udf/inode.c:2383
 udf_table_prealloc_blocks fs/udf/balloc.c:543 [inline]
 udf_prealloc_blocks+0xbd3/0x1130 fs/udf/balloc.c:701
 udf_prealloc_extents fs/udf/inode.c:1060 [inline]
 inode_getblk fs/udf/inode.c:918 [inline]
 udf_map_block+0x1e8a/0x4330 fs/udf/inode.c:454
 __udf_get_block+0x52/0x250 fs/udf/inode.c:468
 __block_write_begin_int+0x6c6/0x1910 fs/buffer.c:2145
 block_write_begin+0x8d/0x120 fs/buffer.c:2256
 udf_write_begin+0x118/0x270 fs/udf/inode.c:262
 generic_perform_write+0x2e2/0x8f0 mm/filemap.c:4314
 udf_file_write_iter+0x2ca/0x6b0 fs/udf/file.c:111
 __kernel_write_iter+0x41e/0x880 fs/read_write.c:619
 dump_emit_page fs/coredump.c:1298 [inline]
 dump_user_range+0xb89/0x12d0 fs/coredump.c:1372
 elf_core_dump+0x34c2/0x3ad0 fs/binfmt_elf.c:2111
 coredump_write+0x1219/0x1950 fs/coredump.c:1049
 do_coredump fs/coredump.c:1126 [inline]
 vfs_coredump+0x369e/0x4270 fs/coredump.c:1200
 get_signal+0x1107/0x1330 kernel/signal.c:3019
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:75 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
 irqentry_exit+0x176/0x620 kernel/entry/common.c:196
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x5bea3
Code: Unable to access opcode bytes at 0x5be79.
RSP: 002b:0000200000000478 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007fd37c015fa0 RCX: 00007fd37bd9aeb9
RDX: 00002000000000c0 RSI: 0000200000000470 RDI: 0000000000001000
RBP: 00007fd37be08c1f R08: 0000200000000480 R09: 0000200000000480
R10: 0000200000000140 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fd37c016038 R14: 00007fd37c015fa0 R15: 00007ffed59fb828
 </TASK>