CVE-2025-37858

/// Technical description

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

fs/jfs: Prevent integer overflow in AG size calculation

The JFS filesystem calculates allocation group (AG) size using 1 <<

l2agsize in dbExtendFS(). When l2agsize exceeds 31 (possible with >2TB

aggregates on 32-bit systems), this 32-bit shift operation causes undefined

behavior and improper AG sizing.

On 32-bit architectures:

- Left-shifting 1 by 32+ bits results in 0 due to integer overflow

- This creates invalid AG sizes (0 or garbage values) in

sbi->bmap->db_agsize

- Subsequent block allocations would reference invalid AG structures

- Could lead to:

- Filesystem corruption during extend operations

- Kernel crashes due to invalid memory accesses

- Security vulnerabilities via malformed on-disk structures

Fix by casting to s64 before shifting:

bmp->db_agsize = (s64)1 << l2agsize;

This ensures 64-bit arithmetic even on 32-bit architectures. The cast

matches the data type of db_agsize (s64) and follows simil

/// 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