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->b…

Overview

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.

Affected

• linux_kernel >= 5.4.293, < 5.5
• linux_kernel >= 5.10.237, < 5.10.258
• linux_kernel >= 5.15.181, < 5.15.209
• linux_kernel >= 6.1.135, < 6.1.175
• linux_kernel >= 6.6.88, < 6.6.140
• linux_kernel >= 6.12.25, < 6.12.88
• linux_kernel >= 6.14.4, < 6.15
• linux_kernel >= 6.15.1, < 6.18.30
• linux_kernel >= 6.19, < 7.0.7
• linux_kernel = 6.15
• linux_kernel = 7.1

Remediation

Upgrade past the affected range:

• linux_kernel 7.0.7