VDB-315930 · CVE-2025-38305 · EUVD-2025-20943

Linux Kernel up to 6.16-rc1 ptp ptp_vclock_in_use deadlock

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5.0	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.16-rc1. It has been declared as critical. Affected is the function ptp_vclock_in_use of the component ptp. The manipulation results in deadlock. This vulnerability is known as CVE-2025-38305. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.16-rc1. Affected is the function ptp_vclock_in_use of the component ptp. The manipulation with an unknown input leads to a deadlock vulnerability. CWE is classifying the issue as CWE-833. The product contains multiple threads or executable segments that are waiting for each other to release a necessary lock, resulting in deadlock. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability is traded as CVE-2025-38305 since 04/16/2025. The exploitability is told to be difficult. Technical details are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 243500 (Amazon Linux 2023 : bpftool, kernel, kernel-devel (ALAS2023-2025-1111)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.186, 6.1.142, 6.6.94, 6.12.34, 6.15.3 or 6.16-rc2 eliminates this vulnerability. Applying the patch 5d217e7031a5c06d366580fc6ddbf43527b780d4/b1b73c452331451020be3bf4b014901015ae6663/259119595227fd20f6aa29d85abe086b6fdd9eb1/b93e6fef4eda48e17d9c642b9abad98a066fd4a3/ef8fc007c28a30a4c0d90bf755e0f343d99bb392/87f7ce260a3c838b49e1dc1ceedf1006795157a2 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (243500), EUVD (EUVD-2025-20943) and CERT Bund (WID-SEC-2025-1522). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

Google Container-Optimized OS
Debian Linux
Amazon Linux 2
Red Hat Enterprise Linux
Ubuntu Linux
SUSE Linux
Oracle Linux
IBM QRadar SIEM
SUSE openSUSE
RESF Rocky Linux
Open Source Linux Kernel
Dell Avamar
Dell NetWorker

Productinfo

Type

Operating System

Vendor

Linux

Name

Kernel

Version

License

open-source

Website

Vendor: https://www.kernel.org/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.1
VulDB Meta Temp Score: 5.0

VulDB Base Score: 4.8
VulDB Temp Score: 4.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CVSSv2info

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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Deadlock
CWE: CWE-833 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒