Bug 2532382 (CVE-2026-89639)

Summary:	CVE-2026-89639 kernel: cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, 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's Common Internet File System (CIFS) implementation. When a file is truncated, the `cifs_do_truncate()` function does not properly invalidate the file system cache (fscache). This oversight can lead to stale cached data being served to users, potentially resulting in information disclosure or data inconsistency.	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 2026-09-11 22:40:15 UTC

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

cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC

cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it
cannot use cifs_resize_file_locked() to perform a proper fscache cookie
resize.  Instead, add cifs_invalidate_cache() after cifs_setsize().

cifs_invalidate_cache() calls fscache_invalidate(), which works without
holding i_rwsem: it unconditionally increments inval_counter and sets
FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not
served once the cookie is later activated by fscache_use_cookie().
Truncation to zero leaves no valid cached data, making invalidation the
correct semantic here.