Silent data corruption bug in CIFS module for write operations affecting kernel ~[6.3-6.9]

[John Cabaj]

SRU Justification

[Impact]

* Microsoft requested patches to fix CIFS module being affected by a silent data corruption bug affecting customers. Only 6.8 kernels are affected, hence the scope being limited to Noble.

[Fix]

* Noble: clean patches from the following upstream LKML submissions (https://lore.kernel.org<email address hidden>/, https://lore.kernel<email address hidden>/):
* "UBUNTU: SAUCE: cifs: stop writeback extension when change of size is detected"
* "UBUNTU: SAUCE: cifs: Fix uncached read into ITER_KVEC iterator"

[Test Plan]

* Compile tested
* Microsoft tested

[Regression potential]

* Changes are localized to CIFS. Possible regressions could result in unexpected behavior of CIFS driver.

[Other info]

* SF#00422224

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-azure/6.8.0-1044.50 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-noble-linux-azure' to 'verification-done-noble-linux-azure'. If the problem still exists, change the tag 'verification-needed-noble-linux-azure' to 'verification-failed-noble-linux-azure'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-azure-fde-6.8/6.8.0-1044.51~22.04.1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-azure-fde-6.8' to 'verification-done-jammy-linux-azure-fde-6.8'. If the problem still exists, change the tag 'verification-needed-jammy-linux-azure-fde-6.8' to 'verification-failed-jammy-linux-azure-fde-6.8'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-azure - 6.8.0-1044.50

---------------
linux-azure (6.8.0-1044.50) noble; urgency=medium

  * noble/linux-azure: 6.8.0-1044.50 -proposed tracker (LP: #2131747)

  * Silent data corruption bug in CIFS module for write operations affecting
    kernel ~[6.3-6.9] (LP: #2131951)
    - SAUCE: cifs: stop writeback extension when change of size is detected
    - SAUCE: cifs: Fix uncached read into ITER_KVEC iterator

  [ Ubuntu: 6.8.0-90.91 ]

  * noble/linux: 6.8.0-90.91 -proposed tracker (LP: #2131785)
  * cifs: Fix memory leak of a folio every call to cifs_writepages_begin()
    (LP: #2131213)
    - cifs: fix pagecache leak when do writepages

  [ Ubuntu: 6.8.0-89.90 ]

  * noble/linux: 6.8.0-89.90 -proposed tracker (LP: #2131481)
  * CVE-2025-39993
    - media: rc: fix races with imon_disconnect()
  * Audio output fails on internal speakers when using kernel 6.8.0-84 and
    newer. (LP: #2130212)
    - Revert "ASoC: cs35l56: Prevent races when soft-resetting using SPI
      control"
  * i40e driver is triggering VF resets on every link state change
    (LP: #2130552)
    - i40e: avoid redundant VF link state updates
  * CVE-2025-40018
    - ipvs: Defer ip_vs_ftp unregister during netns cleanup
  * CVE-2025-39964
    - crypto: af_alg - Disallow concurrent writes in af_alg_sendmsg
    - crypto: af_alg - Fix incorrect boolean values in af_alg_ctx
  * CVE-2025-37958
    - mm/huge_memory: fix dereferencing invalid pmd migration entry
  * CVE-2025-38666
    - net: appletalk: Fix use-after-free in AARP proxy probe

 -- John Cabaj <email address hidden> Fri, 21 Nov 2025 16:00:49 -0600