============================================ WARNING: possible recursive locking detected 4.13.0-mm1+ #7 Not tainted -------------------------------------------- syzkaller025015/2982 is trying to acquire lock: (&grp->list_mutex){++++}, at: [] deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] (&grp->list_mutex){++++}, at: [] snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 but task is already holding lock: (&grp->list_mutex){++++}, at: [] deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] (&grp->list_mutex){++++}, at: [] snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&grp->list_mutex); lock(&grp->list_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by syzkaller025015/2982: #0: (register_mutex#4){+.+.}, at: [] odev_release+0x4a/0x70 sound/core/seq/oss/seq_oss.c:152 #1: (&grp->list_mutex){++++}, at: [] deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] #1: (&grp->list_mutex){++++}, at: [] snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 stack backtrace: CPU: 1 PID: 2982 Comm: syzkaller025015 Not tainted 4.13.0-mm1+ #7 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 print_deadlock_bug kernel/locking/lockdep.c:1797 [inline] check_deadlock kernel/locking/lockdep.c:1844 [inline] validate_chain kernel/locking/lockdep.c:2453 [inline] __lock_acquire+0x1232/0x4620 kernel/locking/lockdep.c:3498 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 down_read+0x96/0x150 kernel/locking/rwsem.c:23 deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 snd_seq_kernel_client_dispatch+0x11e/0x150 sound/core/seq/seq_clientmgr.c:2309 dummy_input+0x2c4/0x400 sound/core/seq/seq_dummy.c:104 snd_seq_deliver_single_event.constprop.11+0x2fb/0x940 sound/core/seq/seq_clientmgr.c:621 deliver_to_subscribers sound/core/seq/seq_clientmgr.c:676 [inline] snd_seq_deliver_event+0x318/0x790 sound/core/seq/seq_clientmgr.c:807 snd_seq_kernel_client_dispatch+0x11e/0x150 sound/core/seq/seq_clientmgr.c:2309 dummy_input+0x2c4/0x400 sound/core/seq/seq_dummy.c:104 snd_seq_deliver_single_event.constprop.11+0x2fb/0x940 sound/core/seq/seq_clientmgr.c:621 snd_seq_deliver_event+0x12c/0x790 sound/core/seq/seq_clientmgr.c:818 snd_seq_kernel_client_dispatch+0x11e/0x150 sound/core/seq/seq_clientmgr.c:2309 snd_seq_oss_dispatch sound/core/seq/oss/seq_oss_device.h:150 [inline] snd_seq_oss_midi_reset+0x44b/0x700 sound/core/seq/oss/seq_oss_midi.c:481 snd_seq_oss_synth_reset+0x398/0x980 sound/core/seq/oss/seq_oss_synth.c:416 snd_seq_oss_reset+0x6c/0x260 sound/core/seq/oss/seq_oss_init.c:448 snd_seq_oss_release+0x71/0x120 sound/core/seq/oss/seq_oss_init.c:425 odev_release+0x52/0x70 sound/core/seq/oss/seq_oss.c:153 __fput+0x333/0x7f0 fs/file_table.c:210 ____fput+0x15/0x20 fs/file_table.c:244 task_work_run+0x199/0x270 kernel/task_work.c:112 exit_task_work include/linux/task_work.h:21 [inline] do_exit+0xa52/0x1b40 kernel/exit.c:865 do_group_exit+0x149/0x400 kernel/exit.c:968 SYSC_exit_group kernel/exit.c:979 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:977 entry_SYSCALL_64_fastpath+0x1f/0xbe RIP: 0033:0x442c58 RSP: 002b:00007fff759563f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000442c58 RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000