CVE-2026-46124

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

isofs: validate block number from NFS file handle in isofs_export_iget

isofs_fh_to_dentry() and isofs_fh_to_parent() pass an attacker-

controlled block number (ifid->block or ifid->parent_block) from

the NFS file handle to isofs_export_iget(), which only rejects

block == 0 before calling isofs_iget() and ultimately sb_bread().

A crafted file handle with fh_len sufficient to pass the check

added by commit 0405d4b63d08 ("isofs: Prevent the use of too small

fid") can still drive the server to read any in-range block on the

backing device as if it were an iso_directory_record. That earlier

fix was assigned CVE-2025-37780.

sb_bread() on an out-of-range block returns NULL cleanly via the

EIO path, so there is no memory-safety violation. For in-range

reads of adjacent-partition data on the same block device, the

unrelated bytes end up in iso_inode_info fields that reach the NFS

client as dentry metadata. The deployment surface (isofs exported

over NFS from loop-mounted images) is narrow and requires an

authenticated NFS peer, but the malformed-file-handle class is

reportable as hardening next to the existing CVE-2025-37780 fix.

Reject block >= ISOFS_SB(sb)->s_nzones in isofs_export_iget() so

the check covers both isofs_fh_to_dentry() and isofs_fh_to_parent()

call sites with a single line.