Bug 2506816 (CVE-2026-64253)

Summary:	CVE-2026-64253 kernel: kernel/fork: clear PF_BLOCK_TS in copy_process()
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel. The `copy_process()` function, responsible for creating new processes, incorrectly inherits a flag (`PF_BLOCK_TS`) from the parent process while simultaneously setting a related pointer (`current->plug`) to null in the child process. This inconsistency can lead to the kernel attempting to access a null pointer without proper validation. A local attacker could potentially exploit this to trigger a system crash, leading to a Denial of Service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-24 16:05:28 UTC

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

kernel/fork: clear PF_BLOCK_TS in copy_process()

PF_BLOCK_TS is only set in blk_time_get_ns() when current->plug is
non-NULL, and blk_finish_plug() clears it via __blk_flush_plug()
before NULLing the plug pointer.  copy_process() breaks the
invariant by inheriting PF_BLOCK_TS from the parent while resetting
the child's plug to NULL.

Clear PF_BLOCK_TS alongside that assignment so callers can rely on
"PF_BLOCK_TS set implies current->plug != NULL" and dereference
current->plug unguarded.

Comment 1 Mauro Matteo Cascella 2026-07-28 12:01:57 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072420-CVE-2026-64253-5b3f@gregkh/T