Bug 2565273 (CVE-2026-99242)

Summary: CVE-2026-99242 kernel: kernel: Information disclosure via race condition between fallocate and mmap reads in NTFS
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: 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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A flaw was found in the Linux kernel's NTFS file system implementation. A race condition between file space preallocation and memory-mapped file operations allows newly allocated storage blocks to be accessed before they are cleared. A local user can exploit this vulnerability by reading memory-mapped files during concurrent space allocation, leading to information disclosure of stale or uninitialized disk 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 2026-11-02 16:45:39 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ntfs: fix race between fallocate and mmap reads

The fallocate implementation only takes invalidate_lock for punch hole,
collapse range, and insert range operations. For standard allocation modes
(mode == 0, FALLOC_FL_KEEP_SIZE), the lock is not held.

During ntfs_attr_fallocate(), new clusters are mapped to the runlist via
ntfs_attr_map_cluster() before being zeroed by ntfs_dio_zero_range(). This
creates a window where concurrent mmap page faults can read uninitialized
disk data.

Since mmap uses filemap_fault() which takes invalidate_lock in shared mode,
it can fault in pages during this window and expose old disk contents to
userspace. This is an information leak and data integrity issue.

Fix by taking invalidate_lock for all fallocate operations, not just for
punch/collapse/insert modes. This prevents concurrent page faults from
accessing unzeroed clusters during the allocation window.