CVE-2026-23238

/// Technical description

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

romfs: check sb_set_blocksize() return value

romfs_fill_super() ignores the return value of sb_set_blocksize(), which

can fail if the requested block size is incompatible with the block

device's configuration.

This can be triggered by setting a loop device's block size larger than

PAGE_SIZE using ioctl(LOOP_SET_BLOCK_SIZE, 32768), then mounting a romfs

filesystem on that device.

When sb_set_blocksize(sb, ROMBSIZE) is called with ROMBSIZE=4096 but the

device has logical_block_size=32768, bdev_validate_blocksize() fails

because the requested size is smaller than the device's logical block

size. sb_set_blocksize() returns 0 (failure), but romfs ignores this and

continues mounting.

The superblock's block size remains at the device's logical block size

(32768). Later, when sb_bread() attempts I/O with this oversized block

size, it triggers a kernel BUG in folio_set_bh():

kernel BUG at fs/buffer.c:1582!

BUG_ON(

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References