Bug 2393192 (CVE-2025-38686)

Summary: CVE-2025-38686 kernel: userfaultfd: fix a crash in UFFDIO_MOVE when PMD is a migration entry
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
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 2025-09-04 16:04:15 UTC 
In the Linux kernel, the following vulnerability has been resolved:

userfaultfd: fix a crash in UFFDIO_MOVE when PMD is a migration entry

When UFFDIO_MOVE encounters a migration PMD entry, it proceeds with
obtaining a folio and accessing it even though the entry is swp_entry_t. 
Add the missing check and let split_huge_pmd() handle migration entries. 
While at it also remove unnecessary folio check.

[surenb: remove extra folio check, per David]
Comment 1 Jon Moroney 2025-09-04 17:37:41 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025090447-CVE-2025-38686-281b@gregkh/T