============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.4.367/7461 is trying to acquire lock:
ffff88802bfe8160 (
&rmidi->open_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline]
&rmidi->open_mutex){+.+.}-{4:4}, at: snd_rawmidi_kernel_open+0xa4/0x190 sound/core/rawmidi.c:422

but task is already holding lock:
ffff8880344a2160 (&rmidi->open_mutex){+.+.}-{4:4}, at: snd_rawmidi_open+0x296/0xba0 sound/core/rawmidi.c:467

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

       CPU0
       ----
  lock(&rmidi->open_mutex);
  lock(&rmidi->open_mutex
);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz.4.367/7461:
 #0: ffff8880344a2160 (&rmidi->open_mutex){+.+.}-{4:4}, at: snd_rawmidi_open+0x296/0xba0 sound/core/rawmidi.c:467
 #1: ffff88802bfe8460 (&ump->open_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline]
 #1: ffff88802bfe8460 (&ump->open_mutex){+.+.}-{4:4}, at: snd_ump_legacy_open+0x120/0x4e0 sound/core/ump.c:1153

stack backtrace:
CPU: 3 UID: 0 PID: 7461 Comm: syz.4.367 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 lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_deadlock_bug.cold+0xbd/0xca kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x1256/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
 class_mutex_constructor include/linux/mutex.h:253 [inline]
 snd_rawmidi_kernel_open+0xa4/0x190 sound/core/rawmidi.c:422
 snd_ump_legacy_open+0x367/0x4e0 sound/core/ump.c:1160
 open_substream+0x480/0x970 sound/core/rawmidi.c:348
 rawmidi_open_priv+0x595/0x6f0 sound/core/rawmidi.c:397
 snd_rawmidi_open+0x4c9/0xba0 sound/core/rawmidi.c:485
 soundcore_open+0x2e3/0x5a0 sound/sound_core.c:594
 chrdev_open+0x234/0x6a0 fs/char_dev.c:411
 do_dentry_open+0x6ab/0x14d0 fs/open.c:947
 vfs_open+0x82/0x3f0 fs/open.c:1052
 do_open fs/namei.c:4700 [inline]
 path_openat+0x2873/0x4280 fs/namei.c:4863
 do_file_open+0x20e/0x430 fs/namei.c:4892
 do_sys_openat2+0x10f/0x1e0 fs/open.c:1368
 do_sys_open fs/open.c:1374 [inline]
 __do_sys_openat fs/open.c:1390 [inline]
 __se_sys_openat fs/open.c:1385 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1385
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4f4775e6ce
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007f4f485b9b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f4f485ba6c0 RCX: 00007f4f4775e6ce
RDX: 0000000000000802 RSI: 00007f4f485b9c00 RDI: ffffffffffffff9c
RBP: 00007f4f485b9c00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: cccccccccccccccd
R13: 00007f4f47a26218 R14: 00007f4f47a26180 R15: 00007ffdf6f11518
 </TASK>