Medium [CVE-2026-68146] Add global mutex to serialize trace_parser access

In the Linux kernel, the following vulnerability has been resolved: ftrace: Add global mutex to serialize trace_parser access In ftrace, the trace_parser structure is allocated and initialized when a trace file is opened, and is subsequently used across write and release handlers to parse user input.

The affected handler paths and their specific functions are: - Open paths: ftrace_regex_open(), ftrace_graph_open() - Write paths: ftrace_regex_write(), ftrace_graph_write() - Release paths: ftrace_regex_release(), ftrace_graph_release() If userspace opens a trace file descriptor and shares it across multiple threads, concurrent write calls will race on the parser's internal state, specifically the 'idx', 'cont', and 'buffer' fields, leading to corrupted input or undefined behavior.

Fix this by adding a global mutex, parser_lock, to serialize all access to trace_parser across write and release paths, preventing concurrent corruption of parser state. A flaw was found in the Linux kernel's ftrace tracing subsystem.

This can result in corrupted input or undefined behavior within the kernel, potentially impacting system stability. This issue affects ftrace when a trace fd is shared across threads.

Concurrent writes race on the per-fd trace_parser without serialization. Systems not using shared trace fds are not affected.