ntfs: fix race between fallocate and mmap reads

Overview

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.

Affected

• Linux >= 495e90fa334828d4119061e2726af51d0a0fb4ed < 7dd1c2fec6ebdd1a88a02cb58ff515a258eeb327
• Linux >= 495e90fa334828d4119061e2726af51d0a0fb4ed < 67aded1da114dc44808315f249bd9e7e440f799d
• Linux 7.1

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.