CVE-2024-57930 in Linux
Summary
by MITRE • 01/21/2025
In the Linux kernel, the following vulnerability has been resolved:
tracing: Have process_string() also allow arrays
In order to catch a common bug where a TRACE_EVENT() TP_fast_assign() assigns an address of an allocated string to the ring buffer and then references it in TP_printk(), which can be executed hours later when the string is free, the function test_event_printk() runs on all events as they are registered to make sure there's no unwanted dereferencing.
It calls process_string() to handle cases in TP_printk() format that has "%s". It returns whether or not the string is safe. But it can have some false positives.
For instance, xe_bo_move() has:
TP_printk("move_lacks_source:%s, migrate object %p [size %zu] from %s to %s device_id:%s",
__entry->move_lacks_source ? "yes" : "no", __entry->bo, __entry->size, xe_mem_type_to_name[__entry->old_placement],
xe_mem_type_to_name[__entry->new_placement], __get_str(device_id))
Where the "%s" references into xe_mem_type_to_name[]. This is an array of
pointers that should be safe for the event to access. Instead of flagging this as a bad reference, if a reference points to an array, where the record field is the index, consider it safe.
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Analysis
by VulDB Data Team • 02/17/2026
The vulnerability described in CVE-2024-57930 resides within the Linux kernel's tracing subsystem, specifically affecting how the process_string() function handles string parameter validation in TRACE_EVENT() macros. This issue represents a false positive detection mechanism designed to prevent use-after-free conditions when tracing events reference allocated strings that may be freed before the trace data is consumed. The tracing infrastructure employs test_event_printk() to validate all events during registration, ensuring that format strings containing "%s" do not inadvertently reference memory that could become invalid. When process_string() encounters a "%s" format specifier, it determines whether the referenced string is safe for later access by checking if it points to allocated memory that might be freed. However, the current implementation fails to properly distinguish between legitimate array-based string references and actual dangerous memory access patterns.
The flaw manifests when tracing events reference array elements containing string pointers, such as the xe_mem_type_to_name[] array in the xe_bo_move() function. In this scenario, the trace event format string references array elements through index-based access where __entry->old_placement and __entry->new_placement serve as array indices. The process_string() function incorrectly flags this safe array access pattern as potentially dangerous because it does not recognize that when a field serves as an array index, the referenced memory location remains stable for the lifetime of the trace event. This false positive occurs because the validation logic does not account for the semantic difference between direct string pointer references and indexed array access patterns that provide stable memory references.
This vulnerability impacts the Linux kernel's ability to properly validate trace event format strings, potentially leading to false security alerts that could cause unnecessary debugging efforts or mask legitimate security issues. The operational impact includes increased false positive rates in kernel tracing validation, which may result in developers spending time investigating non-issues while actual security vulnerabilities could be overlooked. The issue affects systems relying on kernel tracing for debugging, performance monitoring, and security analysis, particularly those using graphics drivers like the xe driver mentioned in the example. From a security perspective, this represents a weakness in the kernel's defensive mechanisms where overly aggressive validation can create false negatives in vulnerability detection, potentially allowing actual use-after-free conditions to go undetected.
The technical implementation flaw stems from the process_string() function's inability to properly analyze the memory access patterns in trace event format strings. When processing "%s" format specifiers, the function should differentiate between direct pointer dereferences that could become invalid and array element access patterns where the referenced memory remains stable. This type of vulnerability aligns with CWE-467 and CWE-470, representing issues with improper handling of array indexing and unsafe string operations. The fix requires modifying the validation logic to recognize that when a trace entry field is used as an array index, the resulting memory access pattern is inherently safe for the duration of the trace event. From an ATT&CK perspective, this vulnerability relates to privilege escalation through kernel exploitation and defense evasion by potentially masking legitimate security issues through false positive detection mechanisms.
The recommended mitigation strategy involves updating the process_string() function to properly analyze the semantic context of array indexing in trace event format strings. The kernel patch should enhance the validation logic to distinguish between direct string pointer access and array element access where field values serve as stable indices. This modification should maintain the core security intent of preventing use-after-free conditions while eliminating false positives that occur with legitimate array-based string references. System administrators should ensure their kernel versions include the patched tracing subsystem to maintain proper security validation without unnecessary false alarms. The fix should be applied across all kernel versions that support the affected tracing infrastructure, particularly those used in production environments where kernel tracing is actively employed for system monitoring and debugging purposes.