Linux Kernel up to 6.6.82/6.12.18/6.13.6 nfs_release_folio deadlock

Summaryinfo

A vulnerability described as critical has been identified in Linux Kernel up to 6.6.82/6.12.18/6.13.6. This issue affects the function nfs_release_folio. Such manipulation leads to deadlock. This vulnerability is documented as CVE-2025-21908. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.6.82/6.12.18/6.13.6. Affected by this issue is the function nfs_release_folio. The manipulation with an unknown input leads to a deadlock vulnerability. Using CWE to declare the problem leads to CWE-833. The product contains multiple threads or executable segments that are waiting for each other to release a necessary lock, resulting in deadlock. Impacted is availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: NFS: fix nfs_release_folio() to not deadlock via kcompactd writeback Add PF_KCOMPACTD flag and current_is_kcompactd() helper to check for it so nfs_release_folio() can skip calling nfs_wb_folio() from kcompactd. Otherwise NFS can deadlock waiting for kcompactd enduced writeback which recurses back to NFS (which triggers writeback to NFSD via NFS loopback mount on the same host, NFSD blocks waiting for XFS's call to __filemap_get_folio): 6070.550357] INFO: task kcompactd0:58 blocked for more than 4435 seconds. {--- [58] "kcompactd0" [] folio_wait_bit+0xe8/0x200 [] folio_wait_writeback+0x2b/0x80 [] nfs_wb_folio+0x80/0x1b0 [nfs] [] nfs_release_folio+0x68/0x130 [nfs] [] split_huge_page_to_list_to_order+0x362/0x840 [] migrate_pages_batch+0x43d/0xb90 [] migrate_pages_sync+0x9a/0x240 [] migrate_pages+0x93c/0x9f0 [] compact_zone+0x8e2/0x1030 [] compact_node+0xdb/0x120 [] kcompactd+0x121/0x2e0 [] kthread+0xcf/0x100 [] ret_from_fork+0x31/0x40 [] ret_from_fork_asm+0x1a/0x30 ---} [[email protected]: fix build]

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2025-21908 since 12/29/2024. The exploitation is known to be difficult. There are known technical details, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 237088 (SUSE SLED15 / SLES15 / openSUSE 15 Security Update : kernel (SUSE-SU-2025:01614-1)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.6.83, 6.12.19 or 6.13.7 eliminates this vulnerability. Applying the patch ab0727d6e2196682351c25c1dd112136f6991f11/5ae31c54cff745832b9bd5b32e71f3d1b607cd1e/8253ff29edcb429a9a6c75710941c6a16a9a34b1/ce6d9c1c2b5cc785016faa11b48b6cd317eb367e 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 (237088) and CERT Bund (WID-SEC-2025-0683). Once again VulDB remains the best source for vulnerability data.

Affected

• Google Container-Optimized OS
• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• RESF Rocky Linux
• Dell Avamar
• Open Source Linux Kernel
• SolarWinds Security Event Manager
• Dell NetWorker
• Dell Secure Connect Gateway
• IBM Security Verify Access

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.6.0
• 6.6.1
• 6.6.2
• 6.6.3
• 6.6.4
• 6.6.5
• 6.6.6
• 6.6.7
• 6.6.8
• 6.6.9
• 6.6.10
• 6.6.11
• 6.6.12
• 6.6.13
• 6.6.14
• 6.6.15
• 6.6.16
• 6.6.17
• 6.6.18
• 6.6.19
• 6.6.20
• 6.6.21
• 6.6.22
• 6.6.23
• 6.6.24
• 6.6.25
• 6.6.26
• 6.6.27
• 6.6.28
• 6.6.29
• 6.6.30
• 6.6.31
• 6.6.32
• 6.6.33
• 6.6.34
• 6.6.35
• 6.6.36
• 6.6.37
• 6.6.38
• 6.6.39
• 6.6.40
• 6.6.41
• 6.6.42
• 6.6.43
• 6.6.44
• 6.6.45
• 6.6.46
• 6.6.47
• 6.6.48
• 6.6.49
• 6.6.50
• 6.6.51
• 6.6.52
• 6.6.53
• 6.6.54
• 6.6.55
• 6.6.56
• 6.6.57
• 6.6.58
• 6.6.59
• 6.6.60
• 6.6.61
• 6.6.62
• 6.6.63
• 6.6.64
• 6.6.65
• 6.6.66
• 6.6.67
• 6.6.68
• 6.6.69
• 6.6.70
• 6.6.71
• 6.6.72
• 6.6.73
• 6.6.74
• 6.6.75
• 6.6.76
• 6.6.77
• 6.6.78
• 6.6.79
• 6.6.80
• 6.6.81
• 6.6.82
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
• 6.12.5
• 6.12.6
• 6.12.7
• 6.12.8
• 6.12.9
• 6.12.10
• 6.12.11
• 6.12.12
• 6.12.13
• 6.12.14
• 6.12.15
• 6.12.16
• 6.12.17
• 6.12.18
• 6.13.0
• 6.13.1
• 6.13.2
• 6.13.3
• 6.13.4
• 6.13.5
• 6.13.6

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Exploitinginfo

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Entryinfo

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