CVE-2022-49322: 
Linux Kernel vulnerability analysis and mitigation

In the Linux kernel, a vulnerability (CVE-2022-49322) was discovered related to tracing functionality when using PREEMPT_RT kernel. The issue occurs when setting bootparams="trace_event=initcall:initcall_start tp_printk=1" in the cmdline. The vulnerability was identified when output_printk() called spin_lock_irqsave() in atomic and irq disable interrupt context situations (Kernel Git).

The technical issue arises because on PREEMPT_RT kernel, the locks are replaced with sleepable rt-spinlock. When spin_lock_irqsave() is called in the atomic and irq disable interrupt context, it triggers a stack calltrace. The bug manifests as a "sleeping function called from invalid context" error at kernel/locking/spinlock_rt.c:46, with in_atomic(): 1, irqs_disabled(): 0, non_block: 0 conditions (NVD).

When triggered, this vulnerability causes a sleeping function to be called from an invalid context in the Linux kernel's tracing subsystem. This can lead to system instability and potential kernel panics, particularly affecting systems running with PREEMPT_RT kernel configurations (Kernel Git).

The issue has been fixed by replacing spin_lock_irqsave() with raw_spin_lock_irqsave() when PREEMPT_RT is enabled and the specific trace events are configured. The fix involves modifying the kernel's trace.c file to use RAW_SPINLOCK instead of regular SPINLOCK for the tracepoint_iter_lock (Kernel Git).