{"id":"CVE-2026-72203","state":"PUBLISHED","title":"ntfs: skip extent mft records in writeback to prevent deadlock","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nntfs: skip extent mft records in writeback to prevent deadlock\n\nThis patch fixes the ABBA deadlock between extent_lock and extent\nmrec_lock triggered by xfstests generic/113, that occurs since the commit\n6994acf33bae (\"ntfs: use base mft_no when looking up base inode for\n\t\textent record\").\n\nPath A (inode writeback):\n  VFS writeback\n    -> ntfs_write_inode()\n      -> __ntfs_write_inode()\n        -> mutex_lock(&ni->extent_lock)\n        -> mutex_lock(&tni->mrec_lock)\n\nPath B (MFT folio writeback):\n  VFS writeback of $MFT dirty folios\n    -> ntfs_mft_writepages()\n      -> ntfs_write_mft_block()\n        -> ntfs_may_write_mft_record()\n          -> holds one extent mrec_lock from a previous iteration\n          -> tries to acquire another base inode extent_lock\n\nBy removing all extent_lock and extent mrec_lock acquisition from the MFT\nfolio writeback path, the ABBA lock ordering is eliminated:\n\nPath A: __ntfs_write_inode(): extent_lock -> mrec_lock\nPath B (removed): ntfs_write_mft_block(): mrec_lock -> extent_lock\n\nPath B is always redundant for extent records because:\n\n1. mark_mft_record_dirty(ext_ni) does NOT dirty the MFT folio.\n   It only sets NInoDirty(ext_ni) and marks the base VFS inode dirty\n   via __mark_inode_dirty(I_DIRTY_DATASYNC), which triggers Path A.\n   Therefore, normal extent modifications never create a situation where\n   the MFT folio is dirty and Path B is not scheduled.\n\n2. The MFT folio only gets dirtied via ntfs_mft_mark_dirty() inside\n   ntfs_mft_record_alloc(). But all identified callers in attrib.c\n   (ntfs_attr_add, ntfs_attr_record_move_away,\n   ntfs_attr_make_non_resident, ntfs_attr_record_resize) follow through\n   with mark_mft_record_dirty(), which triggers Path A to write the\n   complete record.\n\n3. ntfs_evict_big_inode() calls ntfs_commit_inode() before freeing extent\n   inodes, ensuring all dirty extents are flushed via Path A before the\n   base inode leaves the icache.","publishedAt":"2026-08-15T05:54:00.321Z","updatedAt":"2026-10-30T12:28:56.581Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"b06b4fc2138ded8ee0b3dc602991ff6dbb10dd0a","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"6626fb859f4c4772f2f59751d23937716e03f98f","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"7ffa8f3d30236e0ab897c30bdb01224ff1fe1c89","versionType":"git"},{"version":"1e9ea7e04472d4e5e12e58c881eaacfb3e49b669","status":"affected","lessThan":"f831ab09d521898bf1dd99bf5adfd630ea1428e3","versionType":"git"},{"version":"1e9ea7e04472d4e5e12e58c881eaacfb3e49b669","status":"affected","lessThan":"76bc14c7097ff678b2b5dbfd4fa33b46897d87ce","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs/mft.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.12","status":"affected"},{"version":"7.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.12","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.9","status":"unaffected","lessThan":"7.1","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs/mft.c"]}],"references":["https://git.kernel.org/stable/c/b06b4fc2138ded8ee0b3dc602991ff6dbb10dd0a","https://git.kernel.org/stable/c/6626fb859f4c4772f2f59751d23937716e03f98f","https://git.kernel.org/stable/c/7ffa8f3d30236e0ab897c30bdb01224ff1fe1c89","https://git.kernel.org/stable/c/f831ab09d521898bf1dd99bf5adfd630ea1428e3","https://git.kernel.org/stable/c/76bc14c7097ff678b2b5dbfd4fa33b46897d87ce"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72203.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72203","state":"PUBLISHED","datePublished":"2026-08-15T05:54:00.321Z","dateUpdated":"2026-10-30T12:28:56.581Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.912Z"},"containers":{"cna":{"title":"ntfs: skip extent mft records in writeback to prevent deadlock","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nntfs: skip extent mft records in writeback to prevent deadlock\n\nThis patch fixes the ABBA deadlock between extent_lock and extent\nmrec_lock triggered by xfstests generic/113, that occurs since the commit\n6994acf33bae (\"ntfs: use base mft_no when looking up base inode for\n\t\textent record\").\n\nPath A (inode writeback):\n  VFS writeback\n    -> ntfs_write_inode()\n      -> __ntfs_write_inode()\n        -> mutex_lock(&ni->extent_lock)\n        -> mutex_lock(&tni->mrec_lock)\n\nPath B (MFT folio writeback):\n  VFS writeback of $MFT dirty folios\n    -> ntfs_mft_writepages()\n      -> ntfs_write_mft_block()\n        -> ntfs_may_write_mft_record()\n          -> holds one extent mrec_lock from a previous iteration\n          -> tries to acquire another base inode extent_lock\n\nBy removing all extent_lock and extent mrec_lock acquisition from the MFT\nfolio writeback path, the ABBA lock ordering is eliminated:\n\nPath A: __ntfs_write_inode(): extent_lock -> mrec_lock\nPath B (removed): ntfs_write_mft_block(): mrec_lock -> extent_lock\n\nPath B is always redundant for extent records because:\n\n1. mark_mft_record_dirty(ext_ni) does NOT dirty the MFT folio.\n   It only sets NInoDirty(ext_ni) and marks the base VFS inode dirty\n   via __mark_inode_dirty(I_DIRTY_DATASYNC), which triggers Path A.\n   Therefore, normal extent modifications never create a situation where\n   the MFT folio is dirty and Path B is not scheduled.\n\n2. The MFT folio only gets dirtied via ntfs_mft_mark_dirty() inside\n   ntfs_mft_record_alloc(). But all identified callers in attrib.c\n   (ntfs_attr_add, ntfs_attr_record_move_away,\n   ntfs_attr_make_non_resident, ntfs_attr_record_resize) follow through\n   with mark_mft_record_dirty(), which triggers Path A to write the\n   complete record.\n\n3. ntfs_evict_big_inode() calls ntfs_commit_inode() before freeing extent\n   inodes, ensuring all dirty extents are flushed via Path A before the\n   base inode leaves the icache."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"b06b4fc2138ded8ee0b3dc602991ff6dbb10dd0a","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"6626fb859f4c4772f2f59751d23937716e03f98f","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","status":"affected","lessThan":"7ffa8f3d30236e0ab897c30bdb01224ff1fe1c89","versionType":"git"},{"version":"1e9ea7e04472d4e5e12e58c881eaacfb3e49b669","status":"affected","lessThan":"f831ab09d521898bf1dd99bf5adfd630ea1428e3","versionType":"git"},{"version":"1e9ea7e04472d4e5e12e58c881eaacfb3e49b669","status":"affected","lessThan":"76bc14c7097ff678b2b5dbfd4fa33b46897d87ce","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs/mft.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.12","status":"affected"},{"version":"7.1","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.12","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.9","status":"unaffected","lessThan":"7.1","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ntfs/mft.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/b06b4fc2138ded8ee0b3dc602991ff6dbb10dd0a"},{"url":"https://git.kernel.org/stable/c/6626fb859f4c4772f2f59751d23937716e03f98f"},{"url":"https://git.kernel.org/stable/c/7ffa8f3d30236e0ab897c30bdb01224ff1fe1c89"},{"url":"https://git.kernel.org/stable/c/f831ab09d521898bf1dd99bf5adfd630ea1428e3"},{"url":"https://git.kernel.org/stable/c/76bc14c7097ff678b2b5dbfd4fa33b46897d87ce"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The ABBA deadlock is reachable through concurrent VFS writeback on an rw-mounted NTFS volume; ntfs registers ntfs_export_ops, so nfsd/ksmbd remote WRITE/CLOSE/fsync RPCs on an exported NTFS share hit __ntfs_write_inode() and ntfs_mft_writepages() the same as local aio/write syscalls.\nAC:L - xfstests generic/113 (aio-stress with concurrent O_DIRECT/O_SYNC writes) reliably reproduces the hang; an attacker controls both lock-order participants by issuing parallel file metadata writes and sync/writeback pressure without races or attacker-independent memory layout.\nPR:N - Exploitation needs only write access to an rw-mounted or NFS/SMB-exported NTFS volume to drive ntfs_mft_record_alloc and concurrent writeback; no CAP_SYS_ADMIN, root, or init-namespace privileges on the server are required to deadlock the writeback paths.\nUI:N - Once an NTFS volume is rw-mounted (dual-boot partition, removable media, loop mount, or network export), the attacker issues the concurrent writes itself; no additional victim clicks, opens, or cooperative actions are required beyond that standing configuration.\nS:U - The circular mutex wait between extent_lock and extent mrec_lock only hangs kernel writeback and I/O worker threads within the host kernel security authority; it does not cross VM, container, IOMMU, or other security-boundary scopes.\nC:N - This is a deterministic lock-order inversion with no out-of-bounds access, use-after-free, or information disclosure; blocked threads wait on mutexes without reading attacker-controlled freed memory or leaking kernel pointers.\nI:N - The defect prevents completion of metadata writeback by deadlocking mutex acquisition; it does not perform attacker-controlled memory writes, corrupt on-disk NTFS structures, or provide a metadata modification primitive beyond denying forward progress.\nA:H - The ABBA deadlock between inode writeback (extent_lock then extent mrec_lock) and $MFT folio writeback (held mrec_lock then extent_lock) hangs kworker writeback and sync/fsync callers indefinitely, causing system-wide I/O denial of service."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:28:56.581Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.1","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.1","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}