fs/ntfs3: bound DeleteIndexEntryAllocation memmove length

Overview

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

fs/ntfs3: bound DeleteIndexEntryAllocation memmove length

In do_action()'s DeleteIndexEntryAllocation case, e->size comes from an on-disk INDEX_BUFFER entry. When e->size makes e + e->size point past hdr + hdr->used, PtrOffset(e1, Add2Ptr(hdr, used)) returns a negative ptrdiff_t that is silently cast to a quasi-infinite size_t when passed to memmove(). The memmove then walks past the destination buffer.

The sibling DeleteIndexEntryRoot case at fslog.c:3540-3543 already carries the corresponding guard:

if (PtrOffset(e1, Add2Ptr(hdr, used)) < esize ||
    Add2Ptr(e, esize) > Add2Ptr(lrh, rec_len) ||
    used + esize > le32_to_cpu(hdr->total)) {
	goto dirty_vol;
}

Apply the same shape to the allocation-path case. Also reject esize == 0: memmove(e, e, ...) is a no-op and leaves hdr->used unchanged, hiding a malformed entry from the existing check_index_header() walk.

Reproduced under UML+KASAN on mainline 8d90b09e6741 by mounting a crafted NTFS image: the unguarded memmove takes a length of 0xffffffffffffff00 and the kernel oopses in memmove+0x81/0x1a0 on the do_action+0x36a2 frame.

[[email protected]: clang-formatted the changes]

Affected

• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < c38ed2ab62fab75fd6d0fdc2bee540fbebc7b959
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < b509b9613f20dc5b653d54bf78fab00d79cc43c8
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 4c8aac931c1cd70347961ba5157aa916448c6a25
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < f383aae59ec3994c14804f4191c59038b206be81
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 09fddd52c1b0cef2c086d61be8f3d5dc92e36565
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 554700c65d398276cb00a8ef95f1d5e00b9eff93
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < fc4626bb3656362de8b0ecd56605d47a19ec3518
• Linux 5.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.