Bug 2555129 (CVE-2026-98681)

Summary:	CVE-2026-98681 kernel: smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races
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 SMB (Server Message Block) client. Multiple internal file status flags shared the same memory byte without unified locking, creating a race condition during concurrent file operations. A local user performing simultaneous file operations could cause updates to overwrite one another, leading to corrupted file state and a potential denial of service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-10-18 15:56:06 UTC

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

smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races

The invalidHandle, swapfile, oplock_break_cancelled, offload,
and status_file_deleted fields are stored in the same bitfield byte
in struct cifsFileInfo, but are updated in different code paths that
may run simultaneously, and are protected by different locks.  Since
bitfield assignments generate byte-level read-modify-write operations,
a modification to one flag can overwrite a concurrent modification to
another flag.

To avoid these races, convert these flags from a bitfield to
separate bool fields.

Comment 1 Mauro Matteo Cascella 2026-10-22 02:11:28 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98681.mbox