Linux Kernel Function Graph Tracer Argument Handling Vulnerability

A vulnerability in the Linux kernel's function graph tracer has been addressed. When the function graph tracer is not enabled and the 'funcgraph-args' option is set, it incorrectly activates the tracer. This issue arises because the tracer unregisters itself without having been properly registered initially. Consequently, when the tracer is enabled again, it registers a second time, leading to a warning. The vulnerability was observed in version 6.16.0-rc2-test.

Impact

The vulnerability can cause a warning to be triggered in the kernel's tracing subsystem, indicating that the function graph tracer has been registered multiple times incorrectly.

Reproduction

To reproduce this vulnerability, first ensure that the function graph tracer is not enabled. Then, set the 'funcgraph-args' option, which will incorrectly enable the function graph tracer. After this, try to enable the function graph tracer manually, which will result in a write error because the device is busy. This sequence of actions will trigger the warning about the tracer being registered multiple times.