ptp ptp0: new virtual clock ptp1
ptp ptp0: guarantee physical clock free running
ptp ptp0: delete virtual clock ptp1
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/4533 is trying to acquire lock:
ffff0000d9900130 (&clk->rwsem){++++}-{3:3}, at: posix_clock_unregister+0x50/0xb8 kernel/time/posix-clock.c:207

but task is already holding lock:
ffff0000d4119908 (&ptp->n_vclocks_mux){+.+.}-{3:3}, at: n_vclocks_store+0xf4/0x650 drivers/ptp/ptp_sysfs.c:202

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ptp->n_vclocks_mux){+.+.}-{3:3}:
       __mutex_lock_common+0x1a0/0x1f3c kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_interruptible_nested+0x38/0x44 kernel/locking/mutex.c:821
       ptp_vclock_in_use drivers/ptp/ptp_private.h:104 [inline]
       ptp_clock_freerun drivers/ptp/ptp_private.h:121 [inline]
       ptp_clock_adjtime+0x118/0x6f0 drivers/ptp/ptp_clock.c:111
       pc_clock_adjtime+0x1ac/0x238 kernel/time/posix-clock.c:262
       do_clock_adjtime kernel/time/posix-timers.c:1155 [inline]
       __do_sys_clock_adjtime kernel/time/posix-timers.c:1167 [inline]
       __se_sys_clock_adjtime kernel/time/posix-timers.c:1158 [inline]
       __arm64_sys_clock_adjtime+0x29c/0x470 kernel/time/posix-timers.c:1158
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (&clk->rwsem){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3830 [inline]
       __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063
       lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678
       down_write+0x5c/0x88 kernel/locking/rwsem.c:1573
       posix_clock_unregister+0x50/0xb8 kernel/time/posix-clock.c:207
       ptp_clock_unregister+0x190/0x1f0 drivers/ptp/ptp_clock.c:391
       ptp_vclock_unregister+0x100/0x130 drivers/ptp/ptp_vclock.c:230
       unregister_vclock+0xdc/0x14c drivers/ptp/ptp_sysfs.c:164
       device_for_each_child_reverse+0x110/0x1a8 drivers/base/core.c:4073
       n_vclocks_store+0x1ec/0x650 drivers/ptp/ptp_sysfs.c:228
       dev_attr_store+0x6c/0x90 drivers/base/core.c:2388
       sysfs_kf_write+0x1f8/0x274 fs/sysfs/file.c:140
       kernfs_fop_write_iter+0x390/0x4b4 fs/kernfs/file.c:352
       call_write_iter include/linux/fs.h:2271 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x3c8/0x7c8 fs/read_write.c:584
       ksys_write+0x12c/0x228 fs/read_write.c:637
       __do_sys_write fs/read_write.c:649 [inline]
       __se_sys_write fs/read_write.c:646 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
       do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
       el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
       el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

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 ***

4 locks held by syz.0.17/4533:
 #0: ffff0000d96d6460 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x254/0x7c8 fs/read_write.c:580
 #1: ffff0000d4e7e088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1b8/0x4b4 fs/kernfs/file.c:343
 #2: ffff0000d2f64bd0 (kn->active#58){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff0000d2f64bd0 (kn->active#58){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1f8/0x4b4 fs/kernfs/file.c:344
 #3: ffff0000d4119908 (&ptp->n_vclocks_mux){+.+.}-{3:3}, at: n_vclocks_store+0xf4/0x650 drivers/ptp/ptp_sysfs.c:202

stack backtrace:
CPU: 0 PID: 4533 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3830 [inline]
 __lock_acquire+0x2808/0x6634 kernel/locking/lockdep.c:5063
 lock_acquire+0x20c/0x638 kernel/locking/lockdep.c:5678
 down_write+0x5c/0x88 kernel/locking/rwsem.c:1573
 posix_clock_unregister+0x50/0xb8 kernel/time/posix-clock.c:207
 ptp_clock_unregister+0x190/0x1f0 drivers/ptp/ptp_clock.c:391
 ptp_vclock_unregister+0x100/0x130 drivers/ptp/ptp_vclock.c:230
 unregister_vclock+0xdc/0x14c drivers/ptp/ptp_sysfs.c:164
 device_for_each_child_reverse+0x110/0x1a8 drivers/base/core.c:4073
 n_vclocks_store+0x1ec/0x650 drivers/ptp/ptp_sysfs.c:228
 dev_attr_store+0x6c/0x90 drivers/base/core.c:2388
 sysfs_kf_write+0x1f8/0x274 fs/sysfs/file.c:140
 kernfs_fop_write_iter+0x390/0x4b4 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2271 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x3c8/0x7c8 fs/read_write.c:584
 ksys_write+0x12c/0x228 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
ptp ptp0: only physical clock in use now