CVE-2026-72194: fs/ntfs3: add depth limit to indx_find_buffer to prevent stack overflow

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: add depth limit to indx_find_buffer to prevent stack overflow indx_find_buffer() recursively descends the B+ tree index with no depth limit. A crafted NTFS image with circular index node references causes unbounded recursion, overflowing the kernel stack and panicking the system. This is reachable by mounting a malicious NTFS filesystem (e.g. from a USB drive via desktop automount) and deleting a file whose index entry triggers the rebalancing fallback path in indx_delete_entry(). Add a depth parameter and bail out with -EINVAL when it reaches the fnd->nodes array bound, matching the constraint already enforced by fnd_push() in indx_find(). The related function indx_find() was previously patched for a similar infinite-loop issue (commit 1732053c8a6b), but indx_find_buffer() was missed.