tracing: Fix warning in trace_buffered_event_disable()

Summary

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix warning in trace_buffered_event_disable() Warning happened in trace_buffered_event_disable() at WARN_ON_ONCE(!trace_buffered_event_ref) Call Trace: ? __warn+0xa5/0x1b0 ? trace_buffered_event_disable+0x189/0x1b0 __ftrace_event_enable_disable+0x19e/0x3e0 free_probe_data+0x3b/0xa0 unregister_ftrace_function_probe_func+0x6b8/0x800 event_enable_func+0x2f0/0x3d0 ftrace_process_regex.isra.0+0x12d/0x1b0 ftrace_filter_write+0xe6/0x140 vfs_write+0x1c9/0x6f0 [...] The cause of the warning is in __ftrace_event_enable_disable(), trace_buffered_event_enable() was called once while trace_buffered_event_disable() was called twice. Reproduction script show as below, for analysis, see the comments: ``` #!/bin/bash cd /sys/kernel/tracing/ 1. Register a 'disable_event' command, then: 1) SOFT_DISABLED_BIT was set; 2) trace_buffered_event_enable() was called first time; echo 'cmdline_proc_show:disable_event:initcall:initcall_finish' > \ set_ftrace_filter 2. Enable the event registered, then: 1) SOFT_DISABLED_BIT was cleared; 2) trace_buffered_event_disable() was called first time; echo 1 > events/initcall/initcall_finish/enable 3. Try to call into cmdline_proc_show(), then SOFT_DISABLED_BIT was set again!!! cat /proc/cmdline 4. Unregister the 'disable_event' command, then: 1) SOFT_DISABLED_BIT was cleared again; 2) trace_buffered_event_disable() was called second time!!! echo '!cmdline_proc_show:disable_event:initcall:initcall_finish' > \ set_ftrace_filter ``` To fix it, IIUC, we can change to call trace_buffered_event_enable() at fist time soft-mode enabled, and call trace_buffered_event_disable() at last time soft-mode disabled.

Timeline

1. Dec 30, 2025, 12:11 PM UTCCVE published
2. May 11, 2026, 7:57 PM UTCRecord last updated

Affected versions

• Linux Linux

  Version range not reported

• Linux Linux

  4.7

References 8