ptp ptp0: delete virtual clock ptp3 ====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc5-syzkaller #0 Tainted: G U ------------------------------------------------------ syz.1.1207/13482 is trying to acquire lock: ffff88806d20c130 (&clk->rwsem){++++}-{4:4}, at: posix_clock_unregister+0x4d/0xd0 kernel/time/posix-clock.c:184 but task is already holding lock: ffff88814b678868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: n_vclocks_store+0xf1/0x6d0 drivers/ptp/ptp_sysfs.c:215 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&ptp->n_vclocks_mux){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:602 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747 ptp_vclock_in_use drivers/ptp/ptp_private.h:113 [inline] ptp_vclock_in_use drivers/ptp/ptp_private.h:99 [inline] ptp_clock_freerun drivers/ptp/ptp_private.h:130 [inline] ptp_clock_freerun drivers/ptp/ptp_private.h:125 [inline] ptp_clock_adjtime+0x527/0x760 drivers/ptp/ptp_clock.c:125 pc_clock_adjtime+0x115/0x1e0 kernel/time/posix-clock.c:239 do_clock_adjtime kernel/time/posix-timers.c:1162 [inline] __do_sys_clock_adjtime+0x172/0x290 kernel/time/posix-timers.c:1174 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&clk->rwsem){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 down_write+0x92/0x200 kernel/locking/rwsem.c:1577 posix_clock_unregister+0x4d/0xd0 kernel/time/posix-clock.c:184 ptp_clock_unregister+0x14f/0x250 drivers/ptp/ptp_clock.c:432 ptp_vclock_unregister+0x11a/0x160 drivers/ptp/ptp_vclock.c:228 unregister_vclock+0x108/0x1a0 drivers/ptp/ptp_sysfs.c:177 device_for_each_child_reverse+0x133/0x1a0 drivers/base/core.c:4051 n_vclocks_store+0x4b6/0x6d0 drivers/ptp/ptp_sysfs.c:241 dev_attr_store+0x58/0x80 drivers/base/core.c:2440 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c4/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ptp->n_vclocks_mux); lock(&clk->rwsem); lock(&ptp->n_vclocks_mux); lock(&clk->rwsem); *** DEADLOCK *** 5 locks held by syz.1.1207/13482: #0: ffff88806ca63278 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1217 #1: ffff8880314ee428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738 #2: ffff88805a9ba888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325 #3: ffff88814c0025a8 (kn->active#95){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326 #4: ffff88814b678868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: n_vclocks_store+0xf1/0x6d0 drivers/ptp/ptp_sysfs.c:215 stack backtrace: CPU: 0 UID: 0 PID: 13482 Comm: syz.1.1207 Tainted: G U 6.16.0-rc5-syzkaller #0 PREEMPT(full) Tainted: [U]=USER Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 down_write+0x92/0x200 kernel/locking/rwsem.c:1577 posix_clock_unregister+0x4d/0xd0 kernel/time/posix-clock.c:184 ptp_clock_unregister+0x14f/0x250 drivers/ptp/ptp_clock.c:432 ptp_vclock_unregister+0x11a/0x160 drivers/ptp/ptp_vclock.c:228 unregister_vclock+0x108/0x1a0 drivers/ptp/ptp_sysfs.c:177 device_for_each_child_reverse+0x133/0x1a0 drivers/base/core.c:4051 n_vclocks_store+0x4b6/0x6d0 drivers/ptp/ptp_sysfs.c:241 dev_attr_store+0x58/0x80 drivers/base/core.c:2440 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c4/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f6657d8e929 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:00007f6658bbd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f6657fb6080 RCX: 00007f6657d8e929 RDX: 000000000000fdef RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007f6657e10b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f6657fb6080 R15: 00007fff19781418 ptp ptp0: delete virtual clock ptp2 ptp ptp0: delete virtual clock ptp1 ptp ptp0: only physical clock in use now