Linux Kernel: race protect ntfs fallocate/mmap information leak (CVE-2026-99242)
CVE-2026-99242 Published on November 2, 2026
ntfs: fix race between fallocate and mmap reads
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.
Products Associated with CVE-2026-99242
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Affected Versions
Linux:- Version 495e90fa334828d4119061e2726af51d0a0fb4ed and below 7dd1c2fec6ebdd1a88a02cb58ff515a258eeb327 is affected.
- Version 495e90fa334828d4119061e2726af51d0a0fb4ed and below 67aded1da114dc44808315f249bd9e7e440f799d is affected.
- Version 7.1 is affected.
- Before 7.1 is unaffected.
- Version 7.2.14, <= 7.2.* is unaffected.
- Version 7.3, <= * is unaffected.