UBUNTU-CVE-2026-72377: Medium severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: afs: Remove setting of ASRELEASEALWAYS for symlinks and mountpoints Regular AFS files correctly use afsfileaops which have releasefolio set as netfsreleasefolio, so ASRELEASEALWAYS is valid for them when fscache is enabled (set via afsvnodesetcache()). Symlinks and mountpoints in AFS use afsdiraops, which does not provide a releasefolio callback. However, afsapplystatus() unconditionally calls mappingsetreleasealways() for these. In such case when memory management code attempts to release folios, filemapreleasefolio() checks folioneedsrelease() which returns true due to ASRELEASEALWAYS being set. Since there is no releasefolio callback, it falls through to trytofreebuffers(), which at present expects bufferheads to be not null. For symlinks and mountpoints without bufferheads, this causes pointer dereference. [dh: Added more bits that were missed]
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38~24.04.4 - Upgrade
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ubuntu/linux-nvidia-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1024.25~24.04.1 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-38.38 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1008.9 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-nvidia-bosto a version that resolves this vulnerability.Fixed in 7.0.0-2022.23 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1015.15 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-38.38.1 - Configuration
Remove the unconditional mapping_set_release_always() call for AFS symlinks and mountpoints so AS_RELEASE_ALWAYS is not set for them.
Linux kernel AFS AS_RELEASE_ALWAYS = unset for symlinks and mountpoints
Event History
Frequently Asked Questions
Which Ubuntu kernel packages are listed as affected?
The listed packages are ubuntu/linux-riscv, ubuntu/linux-realtime, ubuntu/linux-hwe-edge, ubuntu/linux-azure, ubuntu/linux-gcp, ubuntu/linux-azure-fde, ubuntu/linux-gke, and ubuntu/linux-aws-5.0.
What filesystem objects are involved in the fault?
The issue affects AFS symlinks and mountpoints, which use afs_dir_aops and do not provide a release_folio callback. Regular AFS files use afs_file_aops with netfs_release_folio and are described as correctly handling AS_RELEASE_ALWAYS when fscache is enabled.
What event causes the failure?
When memory management attempts to release folios for affected AFS symlinks or mountpoints, AS_RELEASE_ALWAYS causes the release path to run without a release_folio callback. It can then call try_to_free_buffers() for objects without buffer_heads, resulting in a pointer dereference.