======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc5-syzkaller #0 Tainted: G U
------------------------------------------------------
syz.0.4267/20512 is trying to acquire lock:
ffff88802ffba868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_vclock_in_use drivers/ptp/ptp_private.h:113 [inline]
ffff88802ffba868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_vclock_in_use drivers/ptp/ptp_private.h:99 [inline]
ffff88802ffba868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_clock_freerun drivers/ptp/ptp_private.h:130 [inline]
ffff88802ffba868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_clock_freerun drivers/ptp/ptp_private.h:125 [inline]
ffff88802ffba868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at: ptp_clock_adjtime+0x527/0x760 drivers/ptp/ptp_clock.c:125
but task is already holding lock:
ffff88802ffba130 (&clk->rwsem){++++}-{4:4}, at: get_posix_clock kernel/time/posix-clock.c:25 [inline]
ffff88802ffba130 (&clk->rwsem){++++}-{4:4}, at: get_clock_desc+0x125/0x240 kernel/time/posix-clock.c:209
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&clk->rwsem){++++}-{4:4}:
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
-> #0 (&ptp->n_vclocks_mux){+.+.}-{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
__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
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(&clk->rwsem);
lock(&ptp->n_vclocks_mux);
lock(&clk->rwsem);
lock(&ptp->n_vclocks_mux);
*** DEADLOCK ***
1 lock held by syz.0.4267/20512:
#0: ffff88802ffba130 (&clk->rwsem){++++}-{4:4}, at: get_posix_clock kernel/time/posix-clock.c:25 [inline]
#0: ffff88802ffba130 (&clk->rwsem){++++}-{4:4}, at: get_clock_desc+0x125/0x240 kernel/time/posix-clock.c:209
stack backtrace:
CPU: 0 UID: 0 PID: 20512 Comm: syz.0.4267 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:
<TASK>
__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
__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
RIP: 0033:0x7ffbd478e929
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:00007ffbd5676038 EFLAGS: 00000246 ORIG_RAX: 0000000000000131
RAX: ffffffffffffffda RBX: 00007ffbd49b6080 RCX: 00007ffbd478e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffffb
RBP: 00007ffbd4810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ffbd49b6080 R15: 00007fff4cf8c228
</TASK>