CVE-2023-1077

What it actually does

pick_next_rt_entity() in the Linux kernel scheduler can return a type-confused list_head entry instead of a sched_rt_entity due to an insufficient BUG_ON check, leading to memory corruption when the entry is subsequently dereferenced and used as a real-time scheduling entity.

Why it matters to the business

Linux systems may experience kernel memory corruption that can result in crashes, denial of service, or local privilege escalation, impacting service availability and potentially allowing attackers to gain elevated access on affected hosts.

How an attack unfolds

A local attacker with low privileges crafts conditions that cause the real-time scheduler to invoke pick_next_rt_entity() under a type-confused scenario; the returned list_head is then treated as a sched_rt_entity, corrupting kernel memory structures during scheduling decisions.

How to fix it

Update the Linux kernel to the fixed commit c9852b4dedfce0212d9c06d0d43f04626c6938b1 or later; rebuild and deploy the patched kernel across all affected systems.

How to confirm the fix worked

Verify the running kernel contains commit c9852b4dedfce0212d9c06d0d43f04626c6938b1 via git log or kernel version strings; attempt to reproduce the original type-confusion condition in a test environment to confirm the BUG_ON now correctly detects the error.

Typical attack path

1. Obtain local unprivileged access on a vulnerable Linux system
2. Trigger real-time scheduling paths that exercise pick_next_rt_entity() with crafted task structures
3. Force the BUG_ON check to miss the type confusion
4. Induce subsequent use of the corrupted sched_rt_entity to achieve memory corruption
5. Leverage corruption for privilege escalation or denial of service

How to detect it

Examine kernel logs for unexpected oops or panic messages involving the scheduler or pick_next_rt_entity; review system call traces and audit logs for unusual real-time scheduling activity on systems that may still be vulnerable.

What your security team should do

• Prioritize patching all production Linux kernels to the fixed commit within the next maintenance window
• Monitor upstream kernel changelogs for any related scheduler fixes
• Review real-time scheduling configurations to reduce attack surface where possible
• Apply defense-in-depth measures such as kernel hardening options until patches are deployed