In the Linux kernel, the following vulnerability has been resolved: arm64: ftrace: consistently handle PLTs. Sometimes it is necessary to use a PLT entry to call an ftrace trampoline. This is handled by ftrace_make_call() and ftrace_make_nop(), with each having *almost* identical logic, but this is not handled by ftrace_modify_call() since its introduction in commit: 3b23e4991fb66f6d ("arm64: implement ftrace with regs") Due to this, if we ever were to call ftrace_modify_call() for a callsite which requires a PLT entry for a trampoline, then either: a) If the old addr requires a trampoline, ftrace_modify_call() will use an out-of-range address to generate the 'old' branch instruction. This will result in warnings from aarch64_insn_gen_branch_imm() and ftrace_modify_code(),