CVE-2026-72191

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

ntfs3: validate split-point offset in indxinsertinto_buffer

indxinsertinto_buffer() computes

    used = used1 - tocopy - spsize;

    memmove(det, Add2Ptr(sp, spsize), used - le32tocpu(hdr1->de_off));

where sp and spsize come from hdrfindsplit().  hdrfind_split()

walks entries by le16tocpu(e->size) without validating that each

step stays within hdr->used or that the size field is at least

sizeof(struct NTFSDE).  indexhdr_check(), the on-load gatekeeper,

only validates header-level fields (used, total, de_off) and does

not walk per-entry sizes.

A crafted NTFS image whose leaf INDEX_HDR reports used == total but

contains one interior NTFS_DE with size = 0xFFF0 therefore passes

validation, descends to indxinsertinto_buffer() through the

ntfscreate() -> indxinsertentry() path, and makes hdrfind_split()

return an sp whose sp_size (0xFFF0) greatly exceeds the remaining

bytes in the buffer.  The u32 subtraction underflows and the memmove

count becomes a near-4-GiB value, producing an out-of-bounds kernel

write that corrupts adjacent allocations and panics the kernel.

Reproduced on 7.0.0-rc7 with UML + KASAN via a crafted image and a

single 'touch' inside the mounted directory; crash site resolves to

fs/ntfs3/index.c at the memmove.  Trigger requires only local mount

of an attacker-supplied filesystem image (USB, loopback, or removable

media auto-mount).

Reject the split whenever the chosen sp plus its declared size

already extends past hdr1->used.  This is the minimal fix; it

preserves the existing hdrfindsplit() contract and relies on the

same out: cleanup path as the pre-existing error returns.

A prior OOB read in the very same indxinsertinto_buffer() memmove

was fixed in commit b8c44949044e ("fs/ntfs3: Fix OOB read in

indxinsertintobuffer") by tightening hdrfind_e(), but that fix

does not cover the split-point size field path addressed here: sp is

returned by hdrfindsplit(), not hdrfinde(), and the underflow is

driven by sp->size rather than hdr->used exceeding hdr->total.