In the Linux kernel, the following vulnerability has been resolved: sched/mmcid: Handle vfork()/CLONE_VM correctly Matthieu and Jiri reported stalls where a task endlessly loops in mm_get_cid() when scheduling in. It turned out that the logic which handles vfork()'ed tasks is broken. It is invoked when the number of tasks associated to a process is smaller than the number of MMCID users. It then walks the task list to find the vfork()'ed task, but accounts all the already processed tasks as well. If that double processing brings the number of to be handled tasks to 0, the walk stops and the vfork()'ed task's CID is not fixed up. As a consequence a subsequent schedule in fails to acquire a (transitional) CID and the machine stalls. Cure this by removing the accounting condition and make the fixup always walk the full task list if it could not find the exact number of users in the process' thread list.
History

Fri, 08 May 2026 17:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-665
CWE-730

Fri, 08 May 2026 14:45:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: sched/mmcid: Handle vfork()/CLONE_VM correctly Matthieu and Jiri reported stalls where a task endlessly loops in mm_get_cid() when scheduling in. It turned out that the logic which handles vfork()'ed tasks is broken. It is invoked when the number of tasks associated to a process is smaller than the number of MMCID users. It then walks the task list to find the vfork()'ed task, but accounts all the already processed tasks as well. If that double processing brings the number of to be handled tasks to 0, the walk stops and the vfork()'ed task's CID is not fixed up. As a consequence a subsequent schedule in fails to acquire a (transitional) CID and the machine stalls. Cure this by removing the accounting condition and make the fixup always walk the full task list if it could not find the exact number of users in the process' thread list.
Title sched/mmcid: Handle vfork()/CLONE_VM correctly
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-05-08T14:21:53.618Z

Reserved: 2026-05-01T14:12:56.008Z

Link: CVE-2026-43417

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-05-08T15:16:53.700

Modified: 2026-05-08T15:16:53.700

Link: CVE-2026-43417

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-08T19:15:14Z