CVE-2026-72315: smb: client: fix busy dentry warning on unmount after DIO

Published Aug 15, 2026
·
Updated

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

smb: client: fix busy dentry warning on unmount after DIO

Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed the issue in cifs where deferred close of a file led to a dentry reference count not being released in umount, by flushing deferredclosewq in cifskillsb() to solve it.

However, the cifs DIO path suffers from the same busy-dentry problem caused by a delayed dentry reference-count release:

[dio] [cifsd] [close + umount] netfsunbufferedwriteiterlocked ... cifsdemultiplexthread netfsunbufferedwrite cifsissuewrite netfswaitforinprogressstream [1] ... netfswritesubrequestterminated netfssubreqclearinprogress netfswakecollector // wake [1] netfsputsubrequest netfsputrequest queuework(systemdflwq, xxx) [2] // dio write return cifsclose cifsFileInfoput // cfile->count 2->1 --cfile->count [3]

// umount cifskillsb killanonsuper // warning triggered! shrinkdcacheforumount [4] [systemdflwq] [5] netfsfreerequest ... cifsFileInfoput // cfile->count 1->0 --cfile->count queuework(fileinfoputwq, xxx)

[fileinfoputwq] [6] cifsFileInfoputwork cifsFileInfoputfinal dput

If the umount path is triggered before [5], it results warning: BUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1) [unmount of cifs cifs]

The existing per-inode ictx->iocount wait in cifsevictinode() does not help: it lives in the inode eviction path, which runs after shrinkdcacheforumount() has already warned about the busy dentries.

Fix it by adding a per-superblock outstanding-rreq counter that is incremented in cifsinitrequest() and decremented in cifsfreerequest(). In cifskillsb(), before killanonsuper(), wait for this counter to reach 0 - which guarantees that all cleanupwork for this sb have run and thus all relevant cfile puts are queued on fileinfoputwq or serverclosewq. Then drain the workqueue so the dentry refs are dropped.

This is a targeted wait, not a flush of the system-wide systemdflwq.

Affected Software

163 affected componentsFixes available
Linux Linux kernel
debian/linux<=6.1.176-1, <=6.1.190-1, <=6.12.107-1
6.12.116-17.2.15-17.3.3-1
debian/linux-6.12
6.12.115-2~deb12u1
All of the following
azurelinux/kernel<6.6.159.1-1
6.6.159.1-1
Microsoft Azure Linux=3.0
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<6.8.0-1069.74~22.04.1
6.8.0-1069.74~22.04.1
ubuntu/linux-azure-5.19*
ubuntu/linux-azure-6.2*
ubuntu/linux-azure-6.5*
ubuntu/linux-azure-6.8<6.8.0-1073.82~22.04.1
6.8.0-1073.82~22.04.1
ubuntu/linux-azure-fde-5.19*
ubuntu/linux-azure-fde-6.2*
ubuntu/linux-azure-fde-6.8<6.8.0-1071.78~22.04.1
6.8.0-1071.78~22.04.1
ubuntu/linux-gcp-5.19*
ubuntu/linux-gcp-6.2*
ubuntu/linux-gcp-6.5*
ubuntu/linux-gcp-6.8<6.8.0-1073.81~22.04.1
6.8.0-1073.81~22.04.1
ubuntu/linux-hwe-5.19*
ubuntu/linux-hwe-6.2*
ubuntu/linux-hwe-6.5*
ubuntu/linux-ibm-6.8<6.8.0-1069.70~22.04.1
6.8.0-1069.70~22.04.1
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<6.8.0-149.149.1~22.04.1
6.8.0-149.149.1~22.04.1
ubuntu/linux-nvidia-6.2*
ubuntu/linux-nvidia-6.5*
ubuntu/linux-nvidia-6.8*
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<6.8.0-1067.71~22.04.1
6.8.0-1067.71~22.04.1
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-5.19*
ubuntu/linux-riscv-6.5*
ubuntu/linux-starfive-5.19*
ubuntu/linux-starfive-6.2*
ubuntu/linux-starfive-6.5*
ubuntu/linux-realtime-6.8<6.8.1-1064.65~22.04.1
6.8.1-1064.65~22.04.1
ubuntu/linux<6.8.0-149.149
6.8.0-149.149
ubuntu/linux-aws<6.8.0-1069.74
6.8.0-1069.74
ubuntu/linux-aws-6.14*
ubuntu/linux-aws-6.17*
ubuntu/linux-aws-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-azure<6.8.0-1073.82
6.8.0-1073.82
ubuntu/linux-azure-6.11*
ubuntu/linux-azure-6.14*
ubuntu/linux-azure-6.17*
ubuntu/linux-azure-7.0<7.0.0-1017.17~24.04.1
7.0.0-1017.17~24.04.1
ubuntu/linux-azure-fde*
ubuntu/linux-azure-fde-6.14*
ubuntu/linux-azure-fde-6.17*
ubuntu/linux-azure-fde-7.0<7.0.0-1016.16~24.04.1
7.0.0-1016.16~24.04.1
ubuntu/linux-azure-nvidia*
ubuntu/linux-azure-nvidia-6.14*
ubuntu/linux-gcp<6.8.0-1073.81
6.8.0-1073.81
ubuntu/linux-gcp-6.11*
ubuntu/linux-gcp-6.14*
ubuntu/linux-gcp-7.0<7.0.0-1014.14~24.04.1
7.0.0-1014.14~24.04.1
ubuntu/linux-gke<6.8.0-1068.77
6.8.0-1068.77
ubuntu/linux-gkeop<6.8.0-1053.57
6.8.0-1053.57
ubuntu/linux-hwe-6.11*
ubuntu/linux-hwe-6.14*
ubuntu/linux-hwe-7.0<7.0.0-38.38~24.04.4
7.0.0-38.38~24.04.4
ubuntu/linux-ibm<6.8.0-1069.70
6.8.0-1069.70
ubuntu/linux-lowlatency<6.8.0-149.149.1
6.8.0-149.149.1
ubuntu/linux-lowlatency-hwe-6.11*
ubuntu/linux-nvidia<6.8.0-1067.70
6.8.0-1067.70
ubuntu/linux-nvidia-6.11*
ubuntu/linux-nvidia-7.0<7.0.0-1024.25~24.04.1
7.0.0-1024.25~24.04.1
ubuntu/linux-nvidia-lowlatency*
ubuntu/linux-nvidia-tegra*
ubuntu/linux-oem-6.11*
ubuntu/linux-oem-6.14*
ubuntu/linux-oem-6.8*
ubuntu/linux-oracle<6.8.0-1067.71
6.8.0-1067.71
ubuntu/linux-oracle-6.14*
ubuntu/linux-oracle-7.0<7.0.0-1013.13~24.04.1
7.0.0-1013.13~24.04.1
ubuntu/linux-raspi<6.8.0-1068.72
6.8.0-1068.72
ubuntu/linux-raspi-realtime*
ubuntu/linux-realtime*
ubuntu/linux-riscv*
ubuntu/linux-riscv-6.14*
ubuntu/linux-riscv-6.17*
ubuntu/linux-riscv-7.0<7.0.0-38.38.1~24.04.1
7.0.0-38.38.1~24.04.1
ubuntu/linux-vmware<6.8.0-1010.10
6.8.0-1010.10
ubuntu/linux-xilinx*
ubuntu/linux-bluefield<6.8.0-1036.41
6.8.0-1036.41
ubuntu/linux-raspi-realtime<6.8.0-2056.58
6.8.0-2056.58
ubuntu/linux-realtime<6.8.1-1064.65
6.8.1-1064.65
ubuntu/linux-realtime-6.14*
ubuntu/linux-realtime-6.17*
ubuntu/linux-aws-fips<6.8.0-1069.74+fips1
6.8.0-1069.74+fips1
ubuntu/linux-azure-fips<6.8.0-1073.82+fips1
6.8.0-1073.82+fips1
ubuntu/linux-fips*
ubuntu/linux-gcp-fips<6.8.0-1073.81+fips1
6.8.0-1073.81+fips1
ubuntu/linux<7.0.0-38.38
7.0.0-38.38
ubuntu/linux-aws<7.0.0-1014.14
7.0.0-1014.14
ubuntu/linux-azure<7.0.0-1017.17
7.0.0-1017.17
ubuntu/linux-azure-fde<7.0.0-1016.16
7.0.0-1016.16
ubuntu/linux-gcp<7.0.0-1014.14
7.0.0-1014.14
ubuntu/linux-gke<7.0.0-1008.9
7.0.0-1008.9
ubuntu/linux-ibm<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-nvidia*
ubuntu/linux-nvidia-bos<7.0.0-2022.23
7.0.0-2022.23
ubuntu/linux-oem-7.0<7.0.0-1015.15
7.0.0-1015.15
ubuntu/linux-oracle<7.0.0-1013.13
7.0.0-1013.13
ubuntu/linux-raspi*
ubuntu/linux-realtime<7.0.0-38.38.1
7.0.0-38.38.1
ubuntu/linux-riscv<7.0.0-38.38.1
7.0.0-38.38.1
ubuntu/linux-vmware*

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 6.12.116-1Fixed in 7.2.15-1Fixed in 7.3.3-1
  2. Upgrade

    Upgrade debian/linux-6.12 to a version that resolves this vulnerability.

    Fixed in 6.12.115-2~deb12u1
  3. Upgrade

    Upgrade azurelinux/kernel to a version that resolves this vulnerability.

    Fixed in 6.6.159.1-1
  4. Upgrade

    Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.74~22.04.1
  5. Upgrade

    Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1073.82~22.04.1
  6. Upgrade

    Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1071.78~22.04.1
  7. Upgrade

    Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1073.81~22.04.1
  8. Upgrade

    Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.70~22.04.1
  9. Upgrade

    Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-149.149.1~22.04.1
  10. Upgrade

    Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1067.71~22.04.1
  11. Upgrade

    Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.1-1064.65~22.04.1
  12. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 6.8.0-149.149
  13. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.74
  14. Upgrade

    Upgrade ubuntu/linux-aws-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  15. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 6.8.0-1073.82
  16. Upgrade

    Upgrade ubuntu/linux-azure-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1017.17~24.04.1
  17. Upgrade

    Upgrade ubuntu/linux-azure-fde-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16~24.04.1
  18. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 6.8.0-1073.81
  19. Upgrade

    Upgrade ubuntu/linux-gcp-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14~24.04.1
  20. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 6.8.0-1068.77
  21. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 6.8.0-1053.57
  22. Upgrade

    Upgrade ubuntu/linux-hwe-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38~24.04.4
  23. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.70
  24. Upgrade

    Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-149.149.1
  25. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 6.8.0-1067.70
  26. Upgrade

    Upgrade ubuntu/linux-nvidia-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1024.25~24.04.1
  27. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 6.8.0-1067.71
  28. Upgrade

    Upgrade ubuntu/linux-oracle-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13~24.04.1
  29. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 6.8.0-1068.72
  30. Upgrade

    Upgrade ubuntu/linux-riscv-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1~24.04.1
  31. Upgrade

    Upgrade ubuntu/linux-vmware to a version that resolves this vulnerability.

    Fixed in 6.8.0-1010.10
  32. Upgrade

    Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.

    Fixed in 6.8.0-1036.41
  33. Upgrade

    Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.

    Fixed in 6.8.0-2056.58
  34. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 6.8.1-1064.65
  35. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1069.74+fips1
  36. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1073.82+fips1
  37. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1073.81+fips1
  38. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38
  39. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14
  40. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 7.0.0-1017.17
  41. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 7.0.0-1016.16
  42. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 7.0.0-1014.14
  43. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 7.0.0-1008.9
  44. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  45. Upgrade

    Upgrade ubuntu/linux-nvidia-bos to a version that resolves this vulnerability.

    Fixed in 7.0.0-2022.23
  46. Upgrade

    Upgrade ubuntu/linux-oem-7.0 to a version that resolves this vulnerability.

    Fixed in 7.0.0-1015.15
  47. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 7.0.0-1013.13
  48. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1
  49. Upgrade

    Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.

    Fixed in 7.0.0-38.38.1

Event History

Aug 15, 2026
CVE Published
via MITRE·05:55 AM
Data Sourced
via MITRE·05:55 AM
DescriptionSeverity
Data Sourced
via OSV·06:22 AM
DescriptionSeverityAffected Software
Data Sourced
via NVD·06:22 AM
DescriptionSeverity
Aug 23, 2026
Data Sourced
via Microsoft·10:00 PM
DescriptionSeverityWeakness
Data Sourced
via Microsoft·10:00 PM
Affected Software

Parent advisories

This vulnerability appears in the following advisories.

Peer vulnerabilities

Found alongside the following vulnerabilities.

Frequently Asked Questions

1

What is the severity of CVE-2026-72315?

CVE-2026-72315 has a risk rating of 12, indicating a critical severity level.

2

How do I fix CVE-2026-72315?

To fix CVE-2026-72315, update your Linux kernel to the version that includes the patch for the vulnerability.

3

What system components are affected by CVE-2026-72315?

CVE-2026-72315 affects the SMB client within the Linux kernel.

4

Is there a workaround for CVE-2026-72315?

No specific workaround is recommended for CVE-2026-72315; applying the patch is the best solution.

5

What consequences does CVE-2026-72315 have if exploited?

Exploitation of CVE-2026-72315 could lead to stability issues associated with busy directory entries during unmounting.

Company

Resources

Contact

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