[syzbot] [sound?] possible deadlock in snd_rawmidi_kernel_open

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4235cb24ec1e Merge tag 'vfs-7.2-rc5.fixes' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13f66449580000
kernel config: https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
dashboard link: https://syzkaller.appspot.com/bug?extid=d10d58fc99caa0489796
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-4235cb24.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0220bd6b47b0/vmlinux-4235cb24.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b7fcbec12504/bzImage-4235cb24.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d10d58...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
syzkaller #0 Tainted: G L
--------------------------------------------
syz.5.2143/13505 is trying to acquire lock:
ffff88802becc160 (&rmidi->open_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline]
ffff88802becc160 (&rmidi->open_mutex){+.+.}-{4:4}, at: snd_rawmidi_kernel_open+0xa4/0x190 sound/core/rawmidi.c:422

but task is already holding lock:
ffff888057f60960 (&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.5.2143/13505:
#0: ffff888057f60960 (&rmidi->open_mutex){+.+.}-{4:4}, at: snd_rawmidi_open+0x296/0xba0 sound/core/rawmidi.c:467
#1: ffff88802becc460 (&ump->open_mutex){+.+.}-{4:4}, at: class_mutex_constructor include/linux/mutex.h:253 [inline]
#1: ffff88802becc460 (&ump->open_mutex){+.+.}-{4:4}, at: snd_ump_legacy_open+0x120/0x4e0 sound/core/ump.c:1153

stack backtrace:
CPU: 3 UID: 0 PID: 13505 Comm: syz.5.2143 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
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: 0033:0x7fcac935e6ce
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:00007fcaca1f0b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fcaca1f16c0 RCX: 00007fcac935e6ce
RDX: 0000000000000002 RSI: 00007fcaca1f0c00 RDI: ffffffffffffff9c
RBP: 00007fcaca1f0c00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: cccccccccccccccd
R13: 00007fcac9626038 R14: 00007fcac9625fa0 R15: 00007ffed37eca28
</TASK>


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