CVE-2026-90338

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

serial: amba-pl011: keep console clock enabled for atomic writes

pl011_console_write_atomic() runs from nbcon atomic context, where

sleeping is not allowed. It calls clk_enable(), which takes the common-clk

enable_lock. Under PREEMPT_RT that is a sleeping lock:

clk_enable_lock() first tries spin_trylock_irqsave(), but on contention

falls back to spin_lock_irqsave(). Therefore, an atomic-context printk on

an RT kernel with a clk-backed pl011 can trip:

BUG: sleeping function called from invalid context at spinlock_rt.c:48

__might_resched from rt_spin_lock

rt_spin_lock from clk_enable_lock

clk_enable_lock from clk_enable

clk_enable from pl011_console_write_atomic

... from vprintk_emit

This was found and reproduced on PREEMPT_RT. Arm32 and arm64 DT SoCs are

affected; arm64 SBSA/ACPI has no clk, so clk_enable(NULL) short-circuits

before the lock. In addition, write_atomic() may be invoked from NMI

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References