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CVE-2026-98079

Linux: btrfs: zstd: fix lost wakeup when waiting for a workspace

Linux LinuxOperating systems
Open in ThreatlineRecord JSON
CVSS
NoneNot scored
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.20%Chance of exploitation activity in the next 30 days, higher than 9% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in14d982762945d9945c60bbd48b77df194dd8e28dAlso 844603cf842ee67640d33f350e3fa60f3de7fad3, 0de9f31d447ae71ab08c7850a321682f8d2907c3 and 1 moreCVE List
Published25 Sep 2026Updated 21 Oct 2026CVE List

What fixes it

  • 14d982762945d9945c60bbd48b77df194dd8e28dLinuxCVE List
  • 844603cf842ee67640d33f350e3fa60f3de7fad3LinuxCVE List
  • 0de9f31d447ae71ab08c7850a321682f8d2907c3LinuxCVE List
  • 2acb9f3d1cc8f65dc81ed55e238cbf8e5b60bff7LinuxCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

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

btrfs: zstd: fix lost wakeup when waiting for a workspace

A writer can sleep forever in zstd_get_workspace() even though a workspace is free. When zstd_alloc_workspace() fails, the task is queued on zwsm->wait and schedules unconditionally, never re-testing the pool. zstd_put_workspace() publishes the workspace and then calls cond_wake_up(), which only wakes when a sleeper is already visible, so a workspace returned between the failed allocation and prepare_to_wait() wakes nobody. The window is wide: zstd_alloc_workspace() goes through kvmalloc() and may enter reclaim.

Only a max level workspace triggers the wakeup and one is deliberately kept allocated as the fallback every waiter waits for, so once its wakeup is lost the writer stays in TASK_UNINTERRUPTIBLE until some other task happens to return one. Re-check the pool after prepare_to_wait() has published the waiter, and use the workspace if one turned up.

Text from CVE List

Affected versions 12

  • Linuxaffected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 before 14d982762945d9945c60bbd48b77df194dd8e28dCVE List
  • Linuxaffected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 before 844603cf842ee67640d33f350e3fa60f3de7fad3CVE List
  • Linuxaffected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 before d8f57049521948df5f50797141472fbbed3b0723CVE List
  • Linuxaffected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 before 0de9f31d447ae71ab08c7850a321682f8d2907c3CVE List
  • Linuxaffected: 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96 before 2acb9f3d1cc8f65dc81ed55e238cbf8e5b60bff7CVE List
  • Linuxaffected: 5.1CVE List
  • Linuxunaffected: all versions before 5.1CVE List
  • Linuxunaffected: 6.6.160 through 6.6.*CVE List
  • Linuxunaffected: 6.12.114 through 6.12.*CVE List
  • Linuxunaffected: 6.18.53 through 6.18.*CVE List
  • Linuxunaffected: 7.2.7 through 7.2.*CVE List
  • Linuxunaffected: 7.3CVE List

References 5