Medium [CVE-2026-72353] avoid stale runlist element dereference in fallocate
This medium-severity Red Hat Linux advisory covers CVE-2026-72353.
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Summary
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. 4.
Enter ntfs_filemap_page_mkwrite(). Reach __ntfs_write_iomap_begin() and ntfs_attr_map_cluster().
Merge allocation state with ntfs_runlists_merge(). 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: 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?
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 60 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 60 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 60 minutes ago·verify at source
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