====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.5.788/8434 is trying to acquire lock: ffff8880b8923d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] ffff8880b8923d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168 but task is already holding lock: ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: spin_lock_irq include/linux/spinlock_rt.h:93 [inline] ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: snd_pcm_group_lock_irq sound/core/pcm_native.c:98 [inline] ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: snd_pcm_stream_lock_irq sound/core/pcm_native.c:137 [inline] ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: class_pcm_stream_lock_irq_constructor include/sound/pcm.h:679 [inline] ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: snd_pcm_drop+0x10d/0x270 sound/core/pcm_native.c:2223 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&group->lock#2){+.+.}-{3:3}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:44 [inline] _snd_pcm_stream_lock_irqsave+0x7c/0xa0 sound/core/pcm_native.c:171 class_pcm_stream_lock_irqsave_constructor include/sound/pcm.h:682 [inline] snd_pcm_period_elapsed+0x1e/0x80 sound/core/pcm_lib.c:1938 dummy_hrtimer_callback+0x80/0x180 sound/drivers/dummy.c:386 __run_hrtimer kernel/time/hrtimer.c:1761 [inline] __hrtimer_run_queues+0x54f/0xd40 kernel/time/hrtimer.c:1825 hrtimer_run_softirq+0x1a3/0x2e0 kernel/time/hrtimer.c:1842 handle_softirqs+0x22f/0x710 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1043 smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (&base->softirq_expiry_lock){+...}-{3:3}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:44 [inline] hrtimer_cpu_base_lock_expiry kernel/time/hrtimer.c:1383 [inline] hrtimer_run_softirq+0x7c/0x2e0 kernel/time/hrtimer.c:1838 handle_softirqs+0x22f/0x710 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1043 smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((softirq_ctrl.lock)){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385 __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889 __local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228 hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491 dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410 snd_pcm_do_stop+0x127/0x1c0 sound/core/pcm_native.c:1525 snd_pcm_action_single sound/core/pcm_native.c:1305 [inline] snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388 snd_pcm_stop sound/core/pcm_native.c:1561 [inline] snd_pcm_drop+0x160/0x270 sound/core/pcm_native.c:2228 snd_pcm_oss_sync+0x1de/0xc30 sound/core/oss/pcm_oss.c:1733 snd_pcm_oss_release+0x102/0x250 sound/core/oss/pcm_oss.c:2574 __fput+0x45b/0xa80 fs/file_table.c:468 task_work_run+0x1d4/0x260 kernel/task_work.c:227 get_signal+0x11c5/0x1310 kernel/signal.c:2807 arch_do_signal_or_restart+0x9a/0x750 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop+0x75/0x110 kernel/entry/common.c:40 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: (softirq_ctrl.lock) --> &base->softirq_expiry_lock --> &group->lock#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&group->lock#2); lock(&base->softirq_expiry_lock); lock(&group->lock#2); lock((softirq_ctrl.lock)); *** DEADLOCK *** 2 locks held by syz.5.788/8434: #0: ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: spin_lock_irq include/linux/spinlock_rt.h:93 [inline] #0: ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: snd_pcm_group_lock_irq sound/core/pcm_native.c:98 [inline] #0: ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: snd_pcm_stream_lock_irq sound/core/pcm_native.c:137 [inline] #0: ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: class_pcm_stream_lock_irq_constructor include/sound/pcm.h:679 [inline] #0: ffff88802f946950 (&group->lock#2){+.+.}-{3:3}, at: snd_pcm_drop+0x10d/0x270 sound/core/pcm_native.c:2223 #1: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #1: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #1: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline] #1: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1bb/0x2c0 kernel/locking/spinlock_rt.c:57 stack backtrace: CPU: 1 UID: 0 PID: 8434 Comm: syz.5.788 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385 __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889 __local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228 hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491 dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410 snd_pcm_do_stop+0x127/0x1c0 sound/core/pcm_native.c:1525 snd_pcm_action_single sound/core/pcm_native.c:1305 [inline] snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388 snd_pcm_stop sound/core/pcm_native.c:1561 [inline] snd_pcm_drop+0x160/0x270 sound/core/pcm_native.c:2228 snd_pcm_oss_sync+0x1de/0xc30 sound/core/oss/pcm_oss.c:1733 snd_pcm_oss_release+0x102/0x250 sound/core/oss/pcm_oss.c:2574 __fput+0x45b/0xa80 fs/file_table.c:468 task_work_run+0x1d4/0x260 kernel/task_work.c:227 get_signal+0x11c5/0x1310 kernel/signal.c:2807 arch_do_signal_or_restart+0x9a/0x750 arch/x86/kernel/signal.c:337 exit_to_user_mode_loop+0x75/0x110 kernel/entry/common.c:40 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline] syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline] do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f73c0f0eec9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f73bf16e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: fffffffffffffe00 RBX: 00007f73c1165fa0 RCX: 00007f73c0f0eec9 RDX: 000000000000004f RSI: 0000200000000300 RDI: 0000000000000004 RBP: 00007f73c0f91f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f73c1166038 R14: 00007f73c1165fa0 R15: 00007ffedecd2978