CVE-2023-52791

What it actually does

The flaw performs non-atomic I2C transfers when preemption is disabled, violating the requirement that non-atomic transfers need preemption (e.g., in wait_for_completion), which triggers RCU warnings during panic-driven emergency_restart on I2C restart devices.

Why it matters to the business

Embedded and Android devices using I2C for restart/power functions may log spurious warnings or experience unreliable crash recovery; low ecosystem prevalence limits widespread operational impact.

How an attack unfolds

An attacker triggers a kernel panic on a system where an I2C device handles restart; panic disables preemption, the subsequent I2C xfer incorrectly uses non-atomic paths, and the resulting RCU context-switch violation produces warnings or instability during machine_restart.

How to fix it

Update the Linux kernel to commit 25eb381a736e7ae39a4245ef5c96484eb1073809 or any later stable release that replaces the preemption-disabled check with !preemptible().

How to confirm the fix worked

Confirm the running kernel contains the !preemptible() change in drivers/i2c/i2c-core-base.c and that the RCU warning no longer appears during simulated panic/restart on affected I2C hardware.

Typical attack path

1. Trigger kernel panic via local or remote input
2. panic calls preempt_disable_notrace then emergency_restart
3. I2C restart path attempts non-atomic transfer without preemption
4. RCU detects illegal context switch and emits warnings

How to detect it

Search kernel logs for the exact RCU warning strings and the call chain involving machine_restart, panic, and tegra_i2c_wait_completion or similar I2C completion waits.

• WARNING: CPU:.* at kernel/rcu/tree_plugin.h:.* rcu_note_context_switch
• Voluntary context switch within RCU read-side critical section
• schedule_timeout from wait_for_completion_timeout
• atomic_notifier_call_chain from machine_restart
• machine_restart from panic

What your security team should do

• Apply the fixed kernel commit to all affected stable trees
• Prioritize devices that use I2C for emergency restart
• Add kernel log monitoring for the listed RCU and wait_for_completion warnings
• Re-test panic/restart paths after patching