CVE-2026-72353ntfs: avoid stale runlist element dereference in fallocate

In the Linux kernel, the following vulnerability has been resolved: ntfs: avoid stale runlist element dereference in fallocate ntfs_attr_fallocate() allocates holes and delayed allocations inside initialized size by looking up the current runlist element under ni->runlist.lock. The returned struct runlist_element is only a borrowed pointer into ni->runlist.rl. A writer can replace and free that array after the read lock is dropped, so later reads of rl->lcn, rl->length and rl->vcn can touch freed memory. The buggy scenario involves two paths, with each column showing the order within that path: ntfs_attr_fallocate(): 1. Take ni->runlist.lock for read. 2. Get rl from ntfs_attr_find_vcn_nolock(). 3. Drop ni->runlist.lock. 4. Read rl->lcn, rl->length and rl->vcn. mmap page_mkwrite: 1. Enter ntfs_filemap_page_mkwrite(). 2. Reach __ntfs_write_iomap_begin() and ntfs_attr_map_cluster(). 3. Merge allocation state with ntfs_runlists_merge(). 4. Reallocate ni->runlist.rl in ntfs_rl_realloc(), freeing the old array. Validation reproduced this kernel report: BUG: KASAN: slab-use-after-free in ntfs_attr_fallocate+0xbb8/0xd00 Call Trace: <TASK> dump_stack_lvl+0x66/0xa0 print_report+0xce/0x630 ? ntfs_attr_fallocate+0xbb8/0xd00 ? srso_alias_return_thunk+0x5/0xfbef5 ? __virt_addr_valid+0x20d/0x410 ? ntfs_attr_fallocate+0xbb8/0xd00 kasan_report+0xe0/0x110 ? ntfs_attr_fallocate+0xbb8/0xd00 ntfs_attr_fallocate+0xbb8/0xd00 ? lock_acquire+0x2b8/0x2f0 ? __pfx_ntfs_attr_fallocate+0x10/0x10 ? 0xffffffffc0000095 ? down_write+0x10d/0x1e0 ntfs_fallocate+0x5c9/0x1d00 ? __pfx_ntfs_fallocate+0x10/0x10 ? srso_alias_return_thunk+0x5/0xfbef5 ? lock_acquire+0x2b8/0x2f0 ? srso_alias_return_thunk+0x5/0xfbef5 ? selinux_file_permission+0x3a7/0x510 vfs_fallocate+0x29d/0xd30 __x64_sys_fallocate+0xc7/0x150 ? do_syscall_64+0x81/0x6a0 do_syscall_64+0x115/0x6a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Allocated by task 410: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0xaa/0xb0 __kvmalloc_node_noprof+0x353/0x920 ntfs_rl_realloc+0x3f/0x110 ntfs_runlists_merge+0xaa3/0x3010 ntfs_attr_map_cluster+0x4e5/0xf80 ntfs_attr_fallocate+0x53f/0xd00 ntfs_fallocate+0x5c9/0x1d00 vfs_fallocate+0x29d/0xd30 __x64_sys_fallocate+0xc7/0x150 do_syscall_64+0x115/0x6a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 424: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x5f/0x80 kfree+0x307/0x580 ntfs_rl_realloc+0x6f/0x110 ntfs_runlists_merge+0x7b1/0x3010 ntfs_attr_map_cluster+0x4e5/0xf80 __ntfs_write_iomap_begin+0x8cd/0x2280 iomap_iter+0x6de/0x11e0 iomap_page_mkwrite+0x391/0x650 ntfs_filemap_page_mkwrite+0x1ac/0x400 do_page_mkwrite+0x15c/0x280 __handle_mm_fault+0xd6d/0x1ca0 handle_mm_fault+0x19c/0x470 do_user_addr_fault+0x23b/0x9c0 exc_page_fault+0x5c/0xc0 asm_exc_page_fault+0x26/0x30 Fix this by copying the needed runlist fields while the read lock is still held and using only those scalar snapshots after unlocking. After the snapshot, ntfs_attr_map_cluster() can also find that the range is already mapped and return balloc=false. Only call ntfs_dio_zero_range() when new clusters were allocated, matching the write iomap path and preserving the zero-newly-allocated-holes behavior.

CVSS

8.8 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness (CWE)

Not given

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

Not loaded for this CVE

Assigned by

Linux

NVD analysis

Received

Record last updated

Aug 17, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

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