CVE-2024-27406

What it actually does

The TEST_IOV_ITER Kconfig option lacks a dependency on MMU, allowing the iov_iter unit test to execute on nommu systems where vmap() is unsupported, resulting in a kernel panic at mm/nommu.c.

Why it matters to the business

Kernel crashes during testing on embedded or specialized systems without MMU can disrupt development workflows and require additional configuration checks.

How an attack unfolds

An attacker or tester enables the faulty test module on a nommu kernel, triggering the vmap call and causing a panic.

How to fix it

Update the Linux kernel to the fixed commit e6316749d603fe9c4c91f6ec3694e06e4de632a3 which adds the MMU dependency to TEST_IOV_ITER.

How to confirm the fix worked

Verify the Kconfig entry for TEST_IOV_ITER includes "depends on MMU" after applying the fix.

Typical attack path

1. Enable KUNIT and TEST_IOV_ITER in kernel config
2. Boot on nommu system
3. Run the iov_iter test

How to detect it

Check kernel logs for "BUG: failure at mm/nommu.c:318/vmap()" or "Kernel panic - not syncing: BUG!" during test execution.

• BUG: failure at mm/nommu.c:318/vmap()!
• Kernel panic - not syncing: BUG!

What your security team should do

• Apply the kernel update containing the fix
• Review test configurations for nommu compatibility