Skip to content
OpenAdvisories
High · 7.8 CVE-2025-39881 EUVD-2025-30850GHSA-9jvj-xhwx-w88x

kernfs: Fix UAF in polling when open file is released

Published Sep 23, 2025 · Updated Aug 5, 2026 · Assigned by Linux

Vendor: Linux Product: Linux Package: kernel Package: linux Package: linux Package: linux-allwinner-5.19 Package: linux-aws Package: linux-aws-5.0 Package: linux-aws-5.11 Package: linux-aws-5.13 Package: linux-aws-5.19 Package: linux-aws-5.3 Package: linux-aws-5.8 Package: linux-aws-6.14 Package: linux-aws-6.2 Package: linux-aws-6.5 Package: linux-aws-6.8 Package: linux-aws-fips Package: linux-azure Package: linux-azure-5.11 Package: linux-azure-5.13 Package: linux-azure-5.19 Package: linux-azure-5.3 Package: linux-azure-5.8 Package: linux-azure-6.11 Package: linux-azure-6.14 Package: linux-azure-6.2 Package: linux-azure-6.5 Package: linux-azure-6.8 Package: linux-azure-edge Package: linux-azure-fde Package: linux-azure-fde-5.19 Package: linux-azure-fde-6.14 Package: linux-azure-fde-6.2 Package: linux-azure-fde-6.8 Package: linux-azure-fips Package: linux-azure-nvidia Package: linux-azure-nvidia-6.14 Package: linux-bluefield Package: linux-fips Package: linux-gcp Package: linux-gcp-5.11 Package: linux-gcp-5.13 Package: linux-gcp-5.19 Package: linux-gcp-5.3 Package: linux-gcp-5.8 Package: linux-gcp-6.11 Package: linux-gcp-6.14 Package: linux-gcp-6.2 Package: linux-gcp-6.5 Package: linux-gcp-6.8 Package: linux-gcp-fips Package: linux-gke Package: linux-gke-4.15 Package: linux-gke-5.15 Package: linux-gke-5.4 Package: linux-gkeop Package: linux-gkeop-5.15 Package: linux-gkeop-5.4 Package: linux-hwe Package: linux-hwe-5.11 Package: linux-hwe-5.13 Package: linux-hwe-5.19 Package: linux-hwe-5.8 Package: linux-hwe-6.11 Package: linux-hwe-6.14 Package: linux-hwe-6.2 Package: linux-hwe-6.5 Package: linux-hwe-6.8 Package: linux-hwe-edge Package: linux-ibm Package: linux-ibm-6.8 Package: linux-intel Package: linux-intel-5.13 Package: linux-intel-iot-realtime Package: linux-lowlatency Package: linux-lowlatency-hwe-5.19 Package: linux-lowlatency-hwe-6.11 Package: linux-lowlatency-hwe-6.2 Package: linux-lowlatency-hwe-6.5 Package: linux-lowlatency-hwe-6.8 Package: linux-nvidia Package: linux-nvidia-6.11 Package: linux-nvidia-6.2 Package: linux-nvidia-6.5 Package: linux-nvidia-6.8 Package: linux-nvidia-lowlatency Package: linux-nvidia-tegra Package: linux-oem Package: linux-oem-5.10 Package: linux-oem-5.13 Package: linux-oem-5.14 Package: linux-oem-5.17 Package: linux-oem-5.6 Package: linux-oem-6.0 Package: linux-oem-6.1 Package: linux-oem-6.11 Package: linux-oem-6.14 Package: linux-oem-6.5 Package: linux-oem-6.8 Package: linux-oracle Package: linux-oracle-5.0 Package: linux-oracle-5.11 Package: linux-oracle-5.13 Package: linux-oracle-5.3 Package: linux-oracle-5.8 Package: linux-oracle-6.14 Package: linux-oracle-6.5 Package: linux-oracle-6.8 Package: linux-raspi Package: linux-raspi-realtime Package: linux-raspi2 Package: linux-realtime Package: linux-realtime-6.14 Package: linux-realtime-6.8 Package: linux-riscv Package: linux-riscv-5.11 Package: linux-riscv-5.19 Package: linux-riscv-5.8 Package: linux-riscv-6.14 Package: linux-riscv-6.5 Package: linux-riscv-6.8 Package: linux-starfive-5.19 Package: linux-starfive-6.2 Package: linux-starfive-6.5 Package: linux-vmware Package: linux-xilinx Platform: Linux Ecosystem: Azure Linux Ecosystem: Debian Ecosystem: Ubuntu

Description

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

kernfs: Fix UAF in polling when open file is released

A use-after-free (UAF) vulnerability was identified in the PSI (Pressure
Stall Information) monitoring mechanism:

BUG: KASAN: slab-use-after-free in psi_trigger_poll+0x3c/0x140
Read of size 8 at addr ffff3de3d50bd308 by task systemd/1

psi_trigger_poll+0x3c/0x140
cgroup_pressure_poll+0x70/0xa0
cgroup_file_poll+0x8c/0x100
kernfs_fop_poll+0x11c/0x1c0
ep_item_poll.isra.0+0x188/0x2c0

Allocated by task 1:
cgroup_file_open+0x88/0x388
kernfs_fop_open+0x73c/0xaf0
do_dentry_open+0x5fc/0x1200
vfs_open+0xa0/0x3f0
do_open+0x7e8/0xd08
path_openat+0x2fc/0x6b0
do_filp_open+0x174/0x368

Freed by task 8462:
cgroup_file_release+0x130/0x1f8
kernfs_drain_open_files+0x17c/0x440
kernfs_drain+0x2dc/0x360
kernfs_show+0x1b8/0x288
cgroup_file_show+0x150/0x268
cgroup_pressure_write+0x1dc/0x340
cgroup_file_write+0x274/0x548

Reproduction Steps:
1. Open test/cpu.pressure and establish epoll monitoring
2. Disable monitoring: echo 0 > test/cgroup.pressure
3. Re-enable monitoring: echo 1 > test/cgroup.pressure

The race condition occurs because:
1. When cgroup.pressure is disabled (echo 0 > cgroup.pressure), it:
- Releases PSI triggers via cgroup_file_release()
- Frees of->priv through kernfs_drain_open_files()
2. While epoll still holds reference to the file and continues polling
3. Re-enabling (echo 1 > cgroup.pressure) accesses freed of->priv

epolling disable/enable cgroup.pressure
fd=open(cpu.pressure)
while(1)
...
epoll_wait
kernfs_fop_poll
kernfs_get_active = true echo 0 > cgroup.pressure
... cgroup_file_show
kernfs_show
// inactive kn
kernfs_drain_open_files
cft->release(of);
kfree(ctx);
...
kernfs_get_active = false
echo 1 > cgroup.pressure
kernfs_show
kernfs_activate_one(kn);
kernfs_fop_poll
kernfs_get_active = true
cgroup_file_poll
psi_trigger_poll
// UAF
...
end: close(fd)

To address this issue, introduce kernfs_get_active_of() for kernfs open
files to obtain active references. This function will fail if the open file
has been released. Replace kernfs_get_active() with kernfs_get_active_of()
to prevent further operations on released file descriptors.

Affected products

VendorProductAffectedFixed
Linux Linux 6.1 6.1.153

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 linux 6.16.8-1 —
Debian 13 linux 6.12.48-1 —
Debian 12 linux 6.1.153-1 —
Debian 11 linux-6.1 6.1.153-1~deb11u1 DLA-4328-1
ReleasePackageFixed inAdvisory
Ubuntu Nvidia-BlueField 24.04 LTS linux-bluefield 6.8.0-1017.21 —
Ubuntu 25.10 linux-azure-fde No fix yet —
Ubuntu 24.04 LTS linux 6.8.0-106.106 USN-8095-1
Ubuntu 24.04 LTS linux-aws 6.8.0-1050.53 USN-8095-1
Ubuntu 24.04 LTS linux-azure 6.8.0-1051.57 USN-8125-1
Ubuntu 24.04 LTS linux-azure-fde 6.8.0-1058.65 —
Ubuntu 24.04 LTS linux-azure-nvidia 6.8.0-1039.42 —
Ubuntu 24.04 LTS linux-gcp 6.8.0-1052.55 USN-8095-1
Ubuntu 24.04 LTS linux-gke 6.8.0-1048.53 USN-8095-1
Ubuntu 24.04 LTS linux-gkeop 6.8.0-1035.38 USN-8095-1
Ubuntu 24.04 LTS linux-ibm 6.8.0-1049.49 USN-8095-1
Ubuntu 24.04 LTS linux-intel +19 No fix yet —
Ubuntu 24.04 LTS linux-lowlatency 6.8.0-106.106.1 USN-8095-1
Ubuntu 24.04 LTS linux-nvidia 6.8.0-1049.52 USN-8100-1
Ubuntu 24.04 LTS linux-nvidia-lowlatency 6.8.0-1049.52.1 USN-8100-1
Ubuntu 24.04 LTS linux-nvidia-tegra 6.8.0-1020.20 —
Ubuntu 24.04 LTS linux-oracle 6.8.0-1047.48 USN-8095-1
Ubuntu 24.04 LTS linux-raspi 6.8.0-1050.54 USN-8095-5
Ubuntu 24.04 LTS linux-xilinx 6.8.0-1028.29 USN-8261-1
Ubuntu 22.04 LTS linux-aws-6.8 6.8.0-1050.53~22.04.1 USN-8095-4
Ubuntu 22.04 LTS linux-azure-6.8 6.8.0-1051.57~22.04.1 USN-8126-1
Ubuntu 22.04 LTS linux-azure-fde-6.8 6.8.0-1058.65~22.04.1 —
Ubuntu 22.04 LTS linux-gcp-6.8 6.8.0-1052.55~22.04.1 USN-8095-1
Ubuntu 22.04 LTS linux-hwe-6.8 +1 6.8.0-106.106~22.04.1 USN-8095-1
Ubuntu 22.04 LTS linux-ibm-6.8 6.8.0-1049.49~22.04.1 USN-8095-1
Ubuntu 22.04 LTS linux-lowlatency-hwe-6.8 6.8.0-106.106.1~22.04.1 USN-8095-1
Ubuntu 22.04 LTS linux-nvidia-6.8 6.8.0-1049.52~22.04.1 USN-8100-1
Ubuntu 22.04 LTS linux-oracle-6.8 6.8.0-1047.48~22.04.1 USN-8095-1
Ubuntu 22.04 LTS linux-riscv +32 No fix yet —
Ubuntu 20.04 LTS linux-gke +28 No fix yet —
Show 11 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu 18.04 LTS linux-gcp +14 No fix yet —
Ubuntu 16.04 LTS linux-hwe-edge No fix yet —
Ubuntu Pro Realtime 24.04 LTS linux-raspi-realtime 6.8.0-2040.41 USN-8095-5
Ubuntu Pro Realtime 24.04 LTS linux-realtime 6.8.1-1045.46 USN-8095-3
Ubuntu Pro Realtime 24.04 LTS linux-realtime-6.14 No fix yet —
Ubuntu Pro Realtime 22.04 LTS linux-realtime-6.8 6.8.1-1045.46~22.04.1 USN-8095-3
Ubuntu Pro FIPS-updates 24.04 LTS linux-aws-fips 6.8.0-1050.53+fips1 USN-8095-2
Ubuntu Pro FIPS-updates 24.04 LTS linux-azure-fips 6.8.0-1052.58+fips1 USN-8165-1
Ubuntu Pro FIPS-updates 24.04 LTS linux-fips 6.8.0-106.106+fips1 USN-8095-2
Ubuntu Pro FIPS-updates 24.04 LTS linux-gcp-fips 6.8.0-1052.55+fips1 USN-8095-2
Ubuntu Pro 26.04 LTS linux 7.0.0-30.30 LSN-0122-1
Ubuntu Pro 26.04 LTS linux-aws 7.0.0-1011.11 LSN-0122-1
Ubuntu Pro 26.04 LTS linux-azure 7.0.0-1012.12 LSN-0122-1
Ubuntu Pro 26.04 LTS linux-gcp 7.0.0-1010.10 LSN-0122-1
Ubuntu Pro 24.04 LTS linux 6.8.0-142.142 LSN-0122-1
Ubuntu Pro 24.04 LTS linux-aws 6.8.0-1065.68 LSN-0122-1
Ubuntu Pro 24.04 LTS linux-azure 6.8.0-1068.76 LSN-0122-1
Ubuntu Pro 24.04 LTS linux-gcp 6.8.0-1069.77 LSN-0122-1
Ubuntu Pro 24.04 LTS linux-gke 6.8.0-1064.72 LSN-0122-1
Ubuntu Pro 24.04 LTS linux-ibm 6.8.0-1065.66 LSN-0122-1
Ubuntu Pro 24.04 LTS linux-oracle 6.8.0-1062.65 LSN-0122-1
Ubuntu Pro 22.04 LTS linux 5.15.0-202.212 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-aws 5.15.0-1119.126 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-aws-6.8 6.8.0-1065.68~22.04.1 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-azure 5.15.0-1125.134 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-gcp 5.15.0-1120.130 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-gcp-6.8 6.8.0-1069.77~22.04.1 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-gke 5.15.0-1115.121 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-hwe-6.8 6.8.0-149.149~22.04.1 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-ibm 5.15.0-1113.117 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-ibm-6.8 6.8.0-1066.67~22.04.1 LSN-0122-1
Ubuntu Pro 22.04 LTS linux-lowlatency 5.15.0-197.207 LSN-0122-1
Ubuntu Pro 20.04 LTS linux 5.4.0-245.265 LSN-0122-1
Ubuntu Pro 18.04 LTS linux 4.15.0-260.272 LSN-0122-1
Ubuntu Pro 18.04 LTS linux-aws 4.15.0-1197.210 LSN-0122-1
Ubuntu Pro 18.04 LTS linux-azure-4.15 4.15.0-1207.222 LSN-0122-1
Ubuntu Pro 18.04 LTS linux-gcp-4.15 4.15.0-1190.207 LSN-0122-1
Ubuntu Pro 18.04 LTS linux-hwe-5.4 5.4.0-245.265~18.04.1 LSN-0122-1
Ubuntu Pro 18.04 LTS linux-oracle 4.15.0-1160.171 LSN-0122-1
Ubuntu Pro 16.04 LTS linux 4.4.0-291.325 LSN-0122-1
Ubuntu Pro 16.04 LTS linux-aws 4.4.0-1200.215 LSN-0122-1
Ubuntu Pro 16.04 LTS linux-aws-hwe 4.15.0-1197.210~16.04.1 LSN-0122-1
Ubuntu Pro 16.04 LTS linux-azure 4.15.0-1208.223~16.04.1 LSN-0122-1
Ubuntu Pro 16.04 LTS linux-gcp 4.15.0-1190.207~16.04.1 LSN-0122-1
Ubuntu Pro 16.04 LTS linux-hwe 4.15.0-260.272~16.04.2 LSN-0122-1
ReleasePackageFixed inAdvisory
RHEL 10 kernel-modules-extra-matched 6.12.0-124.9.1.el10_1 RHSA-2025:21118
RHEL 10 rv +77 6.12.0-55.42.1.el10_0 RHSA-2025:21118, RHSA-2025:19469
RHEL 9 rv +75 5.14.0-611.8.1.el9_7 RHSA-2025:21469
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
RHEL 9.6 EUS rv +77 5.14.0-570.69.1.el9_6 RHSA-2025:22392

AlmaLinux

Errata ↗
ReleasePackageFixed inAdvisory
AlmaLinux 10 kernel-doc +1 6.12.0-55.42.1.el10_0 ALSA-2025:19469
ReleasePackageFixed inAdvisory
SLES 15 SP7 kernel-64kb +6 6.4.0-150700.53.22.1 SUSE-SU-2025:4057-1
SLES 15 SP7 kernel-azure +2 6.4.0-150700.20.18.1 SUSE-SU-2025:4132-1
SLES 15 SP7 kernel-default-base 6.4.0-150700.53.22.1.150700.17.15.1 SUSE-SU-2025:4057-1
SLES 15 SP6 kernel-64kb +6 6.4.0-150600.23.78.1 SUSE-SU-2025:4140-1
SLES 15 SP6 kernel-azure +2 6.4.0-150600.8.55.1 SUSE-SU-2025:4128-1
SLES 15 SP6 kernel-default-base 6.4.0-150600.23.78.1.150600.12.34.2 SUSE-SU-2025:4140-1
Show 9 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
SLES for SAP 16.0 kernel-64kb +7 6.12.0-160000.7.1 SUSE-SU-2025:21147-1
SLES for SAP 16.0 kernel-default-base 6.12.0-160000.6.1.160000.2.4 SUSE-SU-2025:21147-1
SLES 16.0 kernel-64kb +7 6.12.0-160000.7.1 SUSE-SU-2025:21180-1, SUSE-SU-2025:21147-1
SLES 16.0 kernel-default-base 6.12.0-160000.6.1.160000.2.4 SUSE-SU-2025:21147-1
SLE Micro 6.2 kernel-default-base 6.12.0-160000.6.1.160000.2.4 SUSE-SU-2025:21080-1
SLE Micro 6.2 kernel-rt +5 6.12.0-160000.7.1 SUSE-SU-2026:20561-1, SUSE-SU-2025:21080-1
SLE Micro 6.1 kernel-default-base 6.4.0-36.1.21.13 SUSE-SU-2025:21056-1
SLE Micro 6.1 kernel-rt +1 6.4.0-38.1 SUSE-SU-2025:21064-1
SLE Micro 6.1 kernel-source +2 6.4.0-36.1 SUSE-SU-2025:21056-1
SLE Micro 6.0 kernel-default-base 6.4.0-36.1.21.13 SUSE-SU-2025:21040-1
SLE Micro 6.0 kernel-rt +1 6.4.0-38.1 SUSE-SU-2025:21052-1
SLE Micro 6.0 kernel-source +2 6.4.0-36.1 SUSE-SU-2025:21040-1
SLE Live Patching 15 SP7 kernel-default 6.4.0-150700.53.22.1 SUSE-SU-2025:4057-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7-RT_Update_6 1-150700.1.3.1 SUSE-SU-2025:4141-1
SLE Live Patching 15 SP7 kernel-livepatch-SLE15-SP7_Update_6 1-150700.15.3.1 SUSE-SU-2025:4057-1
SLE Live Patching 15 SP6 kernel-default 6.4.0-150600.23.78.1 SUSE-SU-2025:4140-1
SLE Live Patching 15 SP6 kernel-livepatch-SLE15-SP6-RT_Update_17 1-150600.1.3.1 SUSE-SU-2025:4301-1
SLE Live Patching 15 SP6 kernel-livepatch-SLE15-SP6_Update_17 1-150600.13.5.1 SUSE-SU-2025:4140-1
SUSE Real Time Module 15 SP7 kernel-rt +2 6.4.0-150700.7.22.1 SUSE-SU-2025:4141-1
SUSE Real Time Module 15 SP6 kernel-rt +3 6.4.0-150600.10.58.1 SUSE-SU-2025:4301-1
ReleasePackageFixed inAdvisory
openSUSE Leap 16.0 kernel-default-base 6.12.0-160000.6.1.160000.2.4 openSUSE-SU-2025:20091-1
openSUSE Leap 16.0 kernel-rt +10 6.12.0-160000.7.1 openSUSE-SU-2025:20091-1
openSUSE Leap 15.6 dtb-aarch64 +10 6.4.0-150600.23.78.1 SUSE-SU-2025:4140-1
openSUSE Leap 15.6 kernel-azure +2 6.4.0-150600.8.55.1 SUSE-SU-2025:4128-1
openSUSE Leap 15.6 kernel-default-base 6.4.0-150600.23.78.1.150600.12.34.2 SUSE-SU-2025:4140-1
openSUSE Leap 15.6 kernel-rt +3 6.4.0-150600.10.58.1 SUSE-SU-2025:4301-1

Amazon Linux

ReleasePackageFixed inAdvisory
Amazon Linux 2023 kernel-livepatch-6.12.48-67.114 +1 1:1.0-0.amzn2023 ALAS2023-2025-1227, ALAS2023-2025-1223
Amazon Linux 2023 perf +14 1:6.1.155-176.282.amzn2023 ALAS2023-2025-1223
Amazon Linux 2023 perf6.12 +14 1:6.12.48-67.114.amzn2023 ALAS2023-2025-1227

Azure Linux

ReleasePackageFixed inAdvisory
Azure Linux 3 kernel 6.6.112.1-1 —

Oracle Linux

ReleasePackageFixed inAdvisory
Oracle Linux 10 kernel-modules-extra-matched 6.12.0-124.13.1.el10_1 ELSA-2025-21118
Oracle Linux 10 rv +28 6.12.0-55.42.1.0.1.el10_0 ELSA-2025-21118, ELSA-2025-19469
Oracle Linux 9 kernel-uek +34 6.12.0-103.40.4.4.el10uek ELSA-2025-25754, ELSA-2025-20719, ELSA-2025-20649
Oracle Linux 9 rv +28 5.14.0-611.8.1.el9_7 ELSA-2025-21469

Advisories 41

References