UBUNTU-CVE-2025-40237: Race Condition

Published Dec 4, 2025

Updated

In the Linux kernel, the following vulnerability has been resolved: fs/notify: call exportfsencodefid with sumount Calling intotifyshowfdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr. This issue was found by syzkaller. Race Condition Diagram: Thread 1 Thread 2 -------- -------- genericshutdownsuper() shrinkdcacheforumount sb->sroot = NULL | | vfsread() | inotifyfdinfo() | inode get from mark | showmarkfhandle(m, inode) | exportfsencodefid(inode, ..) | ovlencodefh(inode, ..) | ovlcheckencodeorigin(inode) | deref isb->sroot | | v fsnotifysbdelete(sb) Which then leads to: [ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUGPAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none) <snip registers, unreliable trace> [ 32.143353] Call Trace: [ 32.143732] ovlencodefh+0xd5/0x170 [ 32.144031] exportfsencodeinodefh+0x12f/0x300 [ 32.144425] showmarkfhandle+0xbe/0x1f0 [ 32.145805] inotifyfdinfo+0x226/0x2d0 [ 32.146442] inotifyshowfdinfo+0x1c5/0x350 [ 32.147168] seqshow+0x530/0x6f0 [ 32.147449] seqreaditer+0x503/0x12a0 [ 32.148419] seqread+0x31f/0x410 [ 32.150714] vfsread+0x1f0/0x9e0 [ 32.152297] ksysread+0x125/0x240 IOW ovlcheckencodeorigin derefs inode->isb->sroot, after it was set to NULL in the unmount path. Fix it by protecting calling exportfsencodefid() from showmarkfhandle() with sumount lock. This form of fix was suggested by Amir in [1]. [1]: https://lore.kernel.org/all/CAOQ4uxhbDwhb+2Brs1UdkoF0a3NSdBAOQPNfEHjahrgoKJpLEw@mail.gmail.com/

Affected Software

147 affected componentsFixes available

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-edge*

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.8*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.8*

ubuntu/linux-intel-5.13*

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.8*

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8<6.8.0-1050.53~22.04.1

6.8.0-1050.53~22.04.1

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8<6.8.0-1051.57~22.04.1

6.8.0-1051.57~22.04.1

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8<6.8.0-1058.65~22.04.1

6.8.0-1058.65~22.04.1

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8<6.8.0-1052.55~22.04.1

6.8.0-1052.55~22.04.1

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-hwe-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-ibm-6.8<6.8.0-1049.49~22.04.1

6.8.0-1049.49~22.04.1

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8<6.8.0-106.106.1~22.04.1

6.8.0-106.106.1~22.04.1

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8<6.8.0-1049.52~22.04.1

6.8.0-1049.52~22.04.1

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8<6.8.0-1047.48~22.04.1

6.8.0-1047.48~22.04.1

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8<6.8.0-106.106~22.04.1

6.8.0-106.106~22.04.1

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-realtime-6.8<6.8.1-1045.46~22.04.1

6.8.1-1045.46~22.04.1

ubuntu/linux<6.8.0-106.106

6.8.0-106.106

ubuntu/linux-aws<6.8.0-1050.53

6.8.0-1050.53

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17<6.17.0-1007.7~24.04.1

6.17.0-1007.7~24.04.1

ubuntu/linux-azure<6.8.0-1051.57

6.8.0-1051.57

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-fde<6.8.0-1058.65

6.8.0-1058.65

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-nvidia<6.8.0-1039.42

6.8.0-1039.42

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1052.55

6.8.0-1052.55

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-6.17<6.17.0-1008.8~24.04.1

6.17.0-1008.8~24.04.1

ubuntu/linux-gke<6.8.0-1048.53

6.8.0-1048.53

ubuntu/linux-gkeop<6.8.0-1035.38

6.8.0-1035.38

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-ibm<6.8.0-1049.49

6.8.0-1049.49

ubuntu/linux-lowlatency<6.8.0-106.106.1

6.8.0-106.106.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia<6.8.0-1049.52

6.8.0-1049.52

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-nvidia-lowlatency<6.8.0-1049.52.1

6.8.0-1049.52.1

ubuntu/linux-nvidia-tegra<6.8.0-1020.20

6.8.0-1020.20

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17<6.17.0-1011.11

6.17.0-1011.11

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1047.48

6.8.0-1047.48

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17<6.17.0-1007.7~24.04.1

6.17.0-1007.7~24.04.1

ubuntu/linux-raspi<6.8.0-1050.54

6.8.0-1050.54

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-xilinx<6.8.0-1028.29

6.8.0-1028.29

ubuntu/linux-bluefield<6.8.0-1017.21

6.8.0-1017.21

ubuntu/linux-raspi-realtime<6.8.0-2040.41

6.8.0-2040.41

ubuntu/linux-realtime<6.8.1-1045.46

6.8.1-1045.46

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17<6.17.0-1006.7~24.04.1

6.17.0-1006.7~24.04.1

ubuntu/linux-aws-fips<6.8.0-1050.53+fips1

6.8.0-1050.53+fips1

ubuntu/linux-azure-fips<6.8.0-1052.58+fips1

6.8.0-1052.58+fips1

ubuntu/linux-fips<6.8.0-106.106+fips1

6.8.0-106.106+fips1

ubuntu/linux-gcp-fips<6.8.0-1052.55+fips1

6.8.0-1052.55+fips1

ubuntu/linux<6.17.0-14.14

6.17.0-14.14

ubuntu/linux-aws<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-azure<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-azure-fde*

ubuntu/linux-gcp<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-oracle<6.17.0-1007.7

6.17.0-1007.7

ubuntu/linux-raspi<6.17.0-1008.8

6.17.0-1008.8

ubuntu/linux-realtime<6.17.0-1006.7

6.17.0-1006.7

ubuntu/linux-riscv<6.17.0-14.14.1

6.17.0-14.14.1

ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1051.57~22.04.1
Upgrade
Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.65~22.04.1
Upgrade
Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55~22.04.1
Upgrade
Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106~22.04.1
Upgrade
Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.49~22.04.1
Upgrade
Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106.1~22.04.1
Upgrade
Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52~22.04.1
Upgrade
Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.48~22.04.1
Upgrade
Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106~22.04.1
Upgrade
Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.
Fixed in 6.8.1-1045.46~22.04.1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53
Upgrade
Upgrade ubuntu/linux-aws-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7~24.04.1
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.8.0-1051.57
Upgrade
Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.
Fixed in 6.8.0-1058.65
Upgrade
Upgrade ubuntu/linux-azure-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1039.42
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55
Upgrade
Upgrade ubuntu/linux-gcp-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8~24.04.1
Upgrade
Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.
Fixed in 6.8.0-1048.53
Upgrade
Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.
Fixed in 6.8.0-1035.38
Upgrade
Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.49
Upgrade
Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106.1
Upgrade
Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52
Upgrade
Upgrade ubuntu/linux-nvidia-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8
Upgrade
Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.
Fixed in 6.8.0-1049.52.1
Upgrade
Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.
Fixed in 6.8.0-1020.20
Upgrade
Upgrade ubuntu/linux-oem-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1011.11
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.8.0-1047.48
Upgrade
Upgrade ubuntu/linux-oracle-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7~24.04.1
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.54
Upgrade
Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.
Fixed in 6.8.0-1028.29
Upgrade
Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.
Fixed in 6.8.0-1017.21
Upgrade
Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.
Fixed in 6.8.0-2040.41
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.8.1-1045.46
Upgrade
Upgrade ubuntu/linux-realtime-6.17 to a version that resolves this vulnerability.
Fixed in 6.17.0-1006.7~24.04.1
Upgrade
Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1050.53+fips1
Upgrade
Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.58+fips1
Upgrade
Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-106.106+fips1
Upgrade
Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.
Fixed in 6.8.0-1052.55+fips1
Upgrade
Upgrade ubuntu/linux to a version that resolves this vulnerability.
Fixed in 6.17.0-14.14
Upgrade
Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7
Upgrade
Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8
Upgrade
Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7
Upgrade
Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.
Fixed in 6.17.0-1007.7
Upgrade
Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.
Fixed in 6.17.0-1008.8
Upgrade
Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.
Fixed in 6.17.0-1006.7
Upgrade
Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.
Fixed in 6.17.0-14.14.1
Compensating control
Protect the call to exportfs_encode_fid() from show_mark_fhandle() with the s_umount lock, so it cannot race with overlayfs unmount and dereference inode->i_sb->s_root after it is set to NULL.

Event History

Dec 4, 2025

CVE Published

via OSV·04:16 PM

Data Sourced

via OSV·04:16 PM

DescriptionSeverityAffected Software

Frequently Asked Questions

Which systems are exposed to this race condition?

The issue affects the listed Ubuntu kernel packages when an inotify file descriptor is watching an OverlayFS inode and the OverlayFS is being unmounted concurrently. Systems that do not use this combination are not described as affected by the provided data.

What access and conditions are needed to trigger it?

The severity vector indicates local access, low privileges, and no user interaction are required. Triggering the issue depends on a race between reading inotify fdinfo for the watched inode and unmounting the OverlayFS.

What is the expected security impact?

The provided vector indicates high availability impact, with no indicated impact to confidentiality or integrity. The described failure is a NULL-pointer dereference that can cause a kernel fault.

UBUNTU-CVE-2025-40237: Race Condition

Affected Software

Remediation

Event History

Frequently Asked Questions

Which systems are exposed to this race condition?

What access and conditions are needed to trigger it?

What is the expected security impact?

Company

Resources

Contact

Frequently Asked Questions

Which systems are exposed to this race condition?

What access and conditions are needed to trigger it?

What is the expected security impact?