============================================ WARNING: possible recursive locking detected 5.15.0-rc6-next-20211022-syzkaller #0 Not tainted -------------------------------------------- syz-executor.4/20075 is trying to acquire lock: ffff888021b709c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_set_volume sound/core/oss/mixer_oss.c:316 [inline] ffff888021b709c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_ioctl1+0x630/0x19a0 sound/core/oss/mixer_oss.c:375 but task is already holding lock: ffff888021b709c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_set_volume sound/core/oss/mixer_oss.c:300 [inline] ffff888021b709c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_ioctl1+0x4b1/0x19a0 sound/core/oss/mixer_oss.c:375 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&mixer->reg_mutex); lock(&mixer->reg_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by syz-executor.4/20075: #0: ffff888021b709c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_set_volume sound/core/oss/mixer_oss.c:300 [inline] #0: ffff888021b709c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_ioctl1+0x4b1/0x19a0 sound/core/oss/mixer_oss.c:375 stack backtrace: CPU: 0 PID: 20075 Comm: syz-executor.4 Not tainted 5.15.0-rc6-next-20211022-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_deadlock_bug kernel/locking/lockdep.c:2956 [inline] check_deadlock kernel/locking/lockdep.c:2999 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027 lock_acquire kernel/locking/lockdep.c:5637 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602 __mutex_lock_common kernel/locking/mutex.c:607 [inline] __mutex_lock+0x12f/0x12f0 kernel/locking/mutex.c:740 snd_mixer_oss_set_volume sound/core/oss/mixer_oss.c:316 [inline] snd_mixer_oss_ioctl1+0x630/0x19a0 sound/core/oss/mixer_oss.c:375 snd_mixer_oss_ioctl+0x40/0x50 sound/core/oss/mixer_oss.c:390 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fe713f24a39 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fe71149a188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fe714027f60 RCX: 00007fe713f24a39 RDX: 0000000020000140 RSI: 00000000c0044d12 RDI: 0000000000000004 RBP: 00007fe713f7ee8f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffe7932e67f R14: 00007fe71149a300 R15: 0000000000022000