CVE-2023-54186

What it actually does

Negative indexing of a buffer array in pin_assignment_show when get_current_pin_assignments returns zero triggers a kernel use-after-free via KASAN-detected bad memory access in the USB Type-C DisplayPort altmode driver.

Why it matters to the business

Low-probability local denial-of-service or privilege-escalation risk on Linux systems handling USB-C video output; widespread kernel deployments amplify potential blast radius if triggered.

How an attack unfolds

A local attacker invokes the sysfs attribute for DisplayPort pin assignments under conditions with no compatible assignments present, causing the driver to perform an out-of-bounds read on already-freed memory.

How to fix it

Upgrade to a kernel containing commit 0e61a7432fcd4bca06f05b7f1c7d7cb461880fe2 or later; apply the stable patch that corrects the indexing check before the buffer access.

How to confirm the fix worked

Confirm the fix commit appears in the kernel tree, verify the patched pin_assignment_show function no longer indexes negatively when zero assignments are returned, and test with USB-C DisplayPort altmode hardware.

Typical attack path

1. Local process reads the pin_assignment_show sysfs attribute
2. get_current_pin_assignments returns zero
3. Code performs negative index into buf array
4. Kernel accesses freed memory resulting in KASAN use-after-free fault

How to detect it

Search kernel logs and KASAN reports for references to pin_assignment_show combined with use-after-free or bad-area faults; correlate with USB Type-C DisplayPort attachment events.

• pin_assignment_show+0x26c/0x33c
• KASAN: use-after-free in pin_assignment_show
• do_bad_area+0x48/0x168

What your security team should do

• Prioritize kernel updates containing 0e61a7432fcd4bca06f05b7f1c7d7cb461880fe2 on all affected Linux hosts
• Monitor kernel logs for KASAN or use-after-free reports involving pin_assignment_show
• Limit untrusted local code execution on systems exposing USB-C DisplayPort functionality until patched