Description
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.