---
id: CVE-2025-38305
title: 'ptp: remove ptp->n_vclocks check logic in ptp_vclock_in_use()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ptp: remove ptp->n_vclocks check logic in ptp_vclock_in_use()

  There is no disagreement that we should check both ptp->is_virtual_clock
  and ptp->n_vclocks to check if t…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 <
    5d217e7031a5c06d366580fc6ddbf43527b780d4
  - >-
    Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 <
    b1b73c452331451020be3bf4b014901015ae6663
  - >-
    Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 <
    259119595227fd20f6aa29d85abe086b6fdd9eb1
  - >-
    Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 <
    b93e6fef4eda48e17d9c642b9abad98a066fd4a3
  - >-
    Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 <
    ef8fc007c28a30a4c0d90bf755e0f343d99bb392
  - >-
    Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 <
    87f7ce260a3c838b49e1dc1ceedf1006795157a2
  - Linux 5.14
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T20:53:36.196517Z'
published: '2025-07-10'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:02:31.571Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-38305'
references:
  - url: 'https://git.kernel.org/stable/c/5d217e7031a5c06d366580fc6ddbf43527b780d4'
  - url: 'https://git.kernel.org/stable/c/b1b73c452331451020be3bf4b014901015ae6663'
  - url: 'https://git.kernel.org/stable/c/259119595227fd20f6aa29d85abe086b6fdd9eb1'
  - url: 'https://git.kernel.org/stable/c/b93e6fef4eda48e17d9c642b9abad98a066fd4a3'
  - url: 'https://git.kernel.org/stable/c/ef8fc007c28a30a4c0d90bf755e0f343d99bb392'
  - url: 'https://git.kernel.org/stable/c/87f7ce260a3c838b49e1dc1ceedf1006795157a2'
tags:
  - cve.org
epss: 0.00179
epssPercentile: 0.07516
ingestedAt: '2026-11-05T22:38:31.949Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

ptp: remove ptp->n_vclocks check logic in ptp_vclock_in_use()

There is no disagreement that we should check both ptp->is_virtual_clock
and ptp->n_vclocks to check if the ptp virtual clock is in use.

However, when we acquire ptp->n_vclocks_mux to read ptp->n_vclocks in
ptp_vclock_in_use(), we observe a recursive lock in the call trace
starting from n_vclocks_store().

============================================
WARNING: possible recursive locking detected
6.15.0-rc6 #1 Not tainted
--------------------------------------------
syz.0.1540/13807 is trying to acquire lock:
ffff888035a24868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at:
 ptp_vclock_in_use drivers/ptp/ptp_private.h:103 [inline]
ffff888035a24868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at:
 ptp_clock_unregister+0x21/0x250 drivers/ptp/ptp_clock.c:415

but task is already holding lock:
ffff888030704868 (&ptp->n_vclocks_mux){+.+.}-{4:4}, at:
 n_vclocks_store+0xf1/0x6d0 drivers/ptp/ptp_sysfs.c:215

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&ptp->n_vclocks_mux);
  lock(&ptp->n_vclocks_mux);

 *** DEADLOCK ***
....
============================================

The best way to solve this is to remove the logic that checks
ptp->n_vclocks in ptp_vclock_in_use().

The reason why this is appropriate is that any path that uses
ptp->n_vclocks must unconditionally check if ptp->n_vclocks is greater
than 0 before unregistering vclocks, and all functions are already
written this way. And in the function that uses ptp->n_vclocks, we
already get ptp->n_vclocks_mux before unregistering vclocks.

Therefore, we need to remove the redundant check for ptp->n_vclocks in
ptp_vclock_in_use() to prevent recursive locking.

## Affected

- `Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 < 5d217e7031a5c06d366580fc6ddbf43527b780d4`
- `Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 < b1b73c452331451020be3bf4b014901015ae6663`
- `Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 < 259119595227fd20f6aa29d85abe086b6fdd9eb1`
- `Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 < b93e6fef4eda48e17d9c642b9abad98a066fd4a3`
- `Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 < ef8fc007c28a30a4c0d90bf755e0f343d99bb392`
- `Linux >= 73f37068d540eba5f93ba3a0019bf479d35ebd76 < 87f7ce260a3c838b49e1dc1ceedf1006795157a2`
- `Linux 5.14`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.