Bug 2555066 (CVE-2026-98685)

Summary: CVE-2026-98685 kernel: smb: client: discard post-EOF pagecache when extending a file via clone range
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: 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   
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Doc Text:
A flaw was found in the Linux kernel's SMB client. This vulnerability can lead to information disclosure when extending a file via a clone range operation. Because the client fails to discard cached memory pages that straddle the original end-of-file boundary, data previously written past the boundary through memory mapping remains visible as valid file content. A local user could exploit this issue to expose sensitive or unintended data.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-10-18 15:52:30 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: discard post-EOF pagecache when extending a file via clone range

cifs_remap_file_range() discarded the pagecache only for the folios
overlapping the destination region, so when a clone extends the file the
folio straddling the old EOF - which may hold data dirtied past EOF
through an mmap - was never dropped and became visible as file content
once the file was extended.

Start the discard at the smaller of fstart and the old EOF.  i_size is
still old here, so nothing past the old EOF is flushed to the server.
Comment 1 Mauro Matteo Cascella 2026-10-22 02:55:47 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98685.mbox