CVE-2021-47315

What it actually does

Failure to release IO memory mapping (fsl_ifc_ctrl_dev->gregs) in the fsl_ifc_ctrl_probe error path leaves the mapping allocated, causing a resource leak.

Why it matters to the business

Repeated probe failures on systems using Freescale IFC controllers can gradually exhaust limited IO mapping resources, leading to reduced stability or functionality in embedded Linux deployments over time.

How an attack unfolds

An attacker with local access could induce repeated driver probe failures through hardware manipulation or module load/unload sequences to trigger the leak and deplete resources, though the error-path-only nature makes remote or reliable exploitation unlikely.

How to fix it

Apply the upstream kernel fix that adds the missing iounmap call for gregs on probe error paths in drivers/memory/fsl_ifc.c.

How to confirm the fix worked

Inspect the fsl_ifc_ctrl_probe function to confirm iounmap is called on all error exits; simulate probe failure scenarios and verify no leaked mappings via /proc/iomem or kernel memory accounting.

Typical attack path

1. Obtain local access or ability to influence driver loading
2. Trigger conditions that cause fsl_ifc probe to fail repeatedly
3. Accumulate unmapped IO resources until system impact occurs

How to detect it

Examine kernel logs for fsl_ifc probe error messages without matching unmap activity; monitor /proc/iomem or vmalloc accounting for unexpected growth tied to the driver.

What your security team should do

• Update affected Linux kernels to include the resource-release fix on any systems using fsl_ifc
• Review embedded device fleets for IFC controller usage and schedule patching
• Add kernel resource-leak monitoring to detect similar issues early