CVE-2026-72203

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

ntfs: skip extent mft records in writeback to prevent deadlock

This patch fixes the ABBA deadlock between extent_lock and extent

mrec_lock triggered by xfstests generic/113, that occurs since the commit

6994acf33bae ("ntfs: use base mft_no when looking up base inode for

extent record").

Path A (inode writeback):

VFS writeback

-> ntfs_write_inode()

-> __ntfs_write_inode()

-> mutex_lock(&ni->extent_lock)

-> mutex_lock(&tni->mrec_lock)

Path B (MFT folio writeback):

VFS writeback of $MFT dirty folios

-> ntfs_mft_writepages()

-> ntfs_write_mft_block()

-> ntfs_may_write_mft_record()

-> holds one extent mrec_lock from a previous iteration

-> tries to acquire another base inode extent_lock

By removing all extent_lock and extent mrec_lock acquisition from the MFT

folio writeback path, the ABBA lock ordering is eliminated:

Path A: __ntfs_write_inode(): extent_lock -> mrec_lock

Path B (removed): ntfs_write_mft_block(): mrec_lock -> extent_lock

Path B is always redundant for extent records because:

1. mark_mft_record_dirty(ext_ni) does NOT dirty the MFT folio.

It only sets NInoDirty(ext_ni) and marks the base VFS inode dirty

via __mark_inode_dirty(I_DIRTY_DATASYNC), which triggers Path A.

Therefore, normal extent modifications never create a situation where

the MFT folio is dirty and Path B is not scheduled.

2. The MFT folio only gets dirtied via ntfs_mft_mark_dirty() inside

ntfs_mft_record_alloc(). But all identified callers in attrib.c

(ntfs_attr_add, ntfs_attr_record_move_away,

ntfs_attr_make_non_resident, ntfs_attr_record_resize) follow through

with mark_mft_record_dirty(), which triggers Path A to write the

complete record.

3. ntfs_evict_big_inode() calls ntfs_commit_inode() before freeing extent

inodes, ensuring all dirty extents are flushed via Path A before the

base inode leaves the icache.