============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.0/5334 is trying to acquire lock:
ffff888013707520 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_free_blocks fs/udf/balloc.c:376 [inline]
ffff888013707520 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_free_blocks+0xa8c/0x1900 fs/udf/balloc.c:678

but task is already holding lock:
ffff888013707520 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_prealloc_blocks fs/udf/balloc.c:517 [inline]
ffff888013707520 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x8ea/0x10e0 fs/udf/balloc.c:702

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.0.0/5334:
 #0: ffff888034948450 (sb_writers#12){.+.+}-{0:0}, at: do_coredump fs/coredump.c:1131 [inline]
 #0: ffff888034948450 (sb_writers#12){.+.+}-{0:0}, at: vfs_coredump+0x36ff/0x44b0 fs/coredump.c:1200
 #1: ffff88805b2d8d00 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #1: ffff88805b2d8d00 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: udf_file_write_iter+0x75/0x6c0 fs/udf/file.c:96
 #2: ffff88805b2d8ae0 (&ei->i_data_sem#3){++++}-{4:4}, at: udf_map_block+0x29c/0x4280 fs/udf/inode.c:445
 #3: ffff888013707520 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_table_prealloc_blocks fs/udf/balloc.c:517 [inline]
 #3: ffff888013707520 (&sbi->s_alloc_mutex){+.+.}-{4:4}, at: udf_prealloc_blocks+0x8ea/0x10e0 fs/udf/balloc.c:702

stack backtrace:
CPU: 0 UID: 0 PID: 5334 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+0x24df/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 udf_table_free_blocks fs/udf/balloc.c:376 [inline]
 udf_free_blocks+0xa8c/0x1900 fs/udf/balloc.c:678
 udf_delete_aext+0x4f5/0xc00 fs/udf/inode.c:2381
 udf_table_prealloc_blocks fs/udf/balloc.c:544 [inline]
 udf_prealloc_blocks+0xbd4/0x10e0 fs/udf/balloc.c:702
 udf_prealloc_extents fs/udf/inode.c:1058 [inline]
 inode_getblk fs/udf/inode.c:916 [inline]
 udf_map_block+0x1e7f/0x4280 fs/udf/inode.c:453
 __udf_get_block+0x52/0x250 fs/udf/inode.c:467
 __block_write_begin_int+0x6c2/0x1900 fs/buffer.c:2123
 block_write_begin+0x8d/0x120 fs/buffer.c:2234
 udf_write_begin+0x118/0x270 fs/udf/inode.c:261
 generic_perform_write+0x2d5/0x8f0 mm/filemap.c:4358
 udf_file_write_iter+0x2e8/0x6c0 fs/udf/file.c:112
 __kernel_write_iter+0x44a/0x8f0 fs/read_write.c:621
 dump_emit_page fs/coredump.c:1298 [inline]
 dump_user_range+0xc19/0x12c0 fs/coredump.c:1372
 elf_core_dump+0x3485/0x3a90 fs/binfmt_elf.c:2109
 coredump_write+0x1290/0x1960 fs/coredump.c:1052
 do_coredump fs/coredump.c:1131 [inline]
 vfs_coredump+0x36ff/0x44b0 fs/coredump.c:1200
 get_signal+0x1094/0x12c0 kernel/signal.c:3031
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:101 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:244 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:315 [inline]
 irqentry_exit+0x2ba/0x8f0 kernel/entry/common.c:165
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
RIP: 0033:0x7ffbca19dea1
Code: 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 48 3d 01 f0 ff ff 73 01 <c3> 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f
RSP: 002b:00000000fffffeb0 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007ffbca425fa0 RCX: 00007ffbca19de99
RDX: 0000000000000000 RSI: 00000000fffffeb0 RDI: 0000000002000400
RBP: 00007ffbca233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007ffbca426038 R14: 00007ffbca425fa0 R15: 00007ffe69fd98c8
 </TASK>