CVE-2023-53007 in Linux
Summary
by MITRE • 03/27/2025
In the Linux kernel, the following vulnerability has been resolved:
tracing: Make sure trace_printk() can output as soon as it can be used
Currently trace_printk() can be used as soon as early_trace_init() is called from start_kernel(). But if a crash happens, and "ftrace_dump_on_oops" is set on the kernel command line, all you get will be:
[ 0.456075] <idle>-0 0dN.2. 347519us : Unknown type 6
[ 0.456075] <idle>-0 0dN.2. 353141us : Unknown type 6
[ 0.456075] <idle>-0 0dN.2. 358684us : Unknown type 6
This is because the trace_printk() event (type 6) hasn't been registered yet. That gets done via an early_initcall(), which may be early, but not early enough.
Instead of registering the trace_printk() event (and other ftrace events, which are not trace events) via an early_initcall(), have them registered at the same time that trace_printk() can be used. This way, if there is a crash before early_initcall(), then the trace_printk()s will actually be useful.
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Analysis
by VulDB Data Team • 12/07/2025
The vulnerability identified as CVE-2023-53007 affects the Linux kernel's tracing subsystem and specifically impacts the trace_printk() function's ability to produce meaningful output during early system initialization and crash scenarios. This issue stems from a timing discrepancy in the kernel's initialization sequence where trace_printk() becomes functionally available before the underlying trace event infrastructure is properly registered. The problem manifests when a system crash occurs and the ftrace_dump_on_oops kernel parameter is enabled, resulting in cryptic error messages such as "Unknown type 6" instead of useful debugging information that could aid in diagnosing the root cause of the failure.
The technical flaw resides in the kernel's early initialization process where the trace_printk() function can be invoked as early as after early_trace_init() is called from start_kernel(), but the registration of the trace_printk() event type occurs through an early_initcall() mechanism that executes at a later stage in the initialization sequence. This temporal mismatch means that when crashes occur during the brief window between when trace_printk() can be called and when the event registration completes, the trace output becomes meaningless because the event type definitions haven't been established yet. The event type 6 specifically represents the trace_printk() event, and without proper registration, the ftrace subsystem cannot properly interpret or display the trace data, leading to the confusing "Unknown type 6" messages that provide no actionable debugging information.
The operational impact of this vulnerability significantly reduces the effectiveness of kernel crash analysis and debugging capabilities, particularly in production environments where system reliability is paramount. When system administrators or developers encounter kernel crashes, they expect to see meaningful trace information that can help identify the cause of failure. Instead, they receive incomprehensible output that obscures the actual problem, potentially extending debugging time and complicating incident response. This vulnerability affects systems where ftrace_dump_on_oops is enabled, which is commonly used in embedded systems, server environments, and development workstations where kernel debugging is essential for maintaining system stability and performance. The issue is particularly problematic because it occurs during critical early boot phases or crash scenarios where diagnostic information is most needed for troubleshooting.
The fix implemented addresses this timing issue by ensuring that trace_printk() event registration occurs simultaneously with when the function becomes available for use, rather than deferring registration to a later early_initcall phase. This approach aligns with the principle of ensuring that kernel debugging facilities are fully functional when they become accessible to prevent situations where diagnostic capabilities are partially broken. The solution follows security best practices by ensuring complete system observability during critical initialization phases and crash scenarios, which is essential for maintaining system integrity and providing adequate forensic data for incident analysis. This change helps satisfy requirements under security frameworks such as those outlined in the Common Weakness Enumeration (CWE) category 117 for inadequate logging and the MITRE ATT&CK framework's T1562.001 technique for disabling or modifying system protection mechanisms, as proper tracing ensures that system protections can be effectively monitored and analyzed during security incidents. The fix ensures that kernel developers and system administrators can rely on trace_printk() output for debugging purposes even when crashes occur during early system initialization, thereby improving overall system reliability and maintainability.