Linux Kernel PLT Handling Vulnerability in Ftrace on ARM64

A vulnerability in the Linux kernel's ftrace implementation for ARM64 architecture has been identified. The issue arises from inconsistent handling of Procedure Linkage Table (PLT) entries when modifying ftrace call sites. This can lead to internal ftrace errors, and in some cases, a kernel panic. The vulnerability occurs in versions of the Linux kernel that include the problematic ftrace_modify_call() function, introduced in a specific commit.

Impact

Exploitation of this vulnerability causes internal ftrace errors, which can disrupt the ftrace functionality without affecting the overall system performance. However, in certain scenarios, it can lead to a kernel panic.

Reproduction

The vulnerability can be reproduced by loading an out-of-tree test module that triggers the ftrace_modify_call() function. This can be done by insmoding the test_ftrace.ko module, which will attempt to modify an ftrace call site that requires a PLT entry. The process will generate warnings about out-of-range branch offsets, indicating the failure to properly modify the call site. This failure can cause subsequent internal ftrace errors, which are logged but typically do not impact the rest of the system.