Bug 2373344 (CVE-2025-38058)

Summary: CVE-2025-38058 kernel: __legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount_lock
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: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
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 2025-06-18 10:02:40 UTC 
In the Linux kernel, the following vulnerability has been resolved:

__legitimize_mnt(): check for MNT_SYNC_UMOUNT should be under mount_lock

... or we risk stealing final mntput from sync umount - raising mnt_count
after umount(2) has verified that victim is not busy, but before it
has set MNT_SYNC_UMOUNT; in that case __legitimize_mnt() doesn't see
that it's safe to quietly undo mnt_count increment and leaves dropping
the reference to caller, where it'll be a full-blown mntput().

Check under mount_lock is needed; leaving the current one done before
taking that makes no sense - it's nowhere near common enough to bother
with.
Comment 1 Avinash Hanwate 2025-06-20 20:56:59 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025061834-CVE-2025-38058-fe06@gregkh/T