In the Linux kernel, the following vulnerability has been resolved: ARM: 9481/2: breakpoint: CFI breakpoints only on demand This removes the stub hw_breakpoint_cfi_handler() from ARM, making it not steal breakpoint type 0x03 (ARM_ENTRY_CFI_BREAKPOINT) unless CFI is actively used in the kernel. When not instrumenting with CFI, or when a breakpoint is issued in userspace, we fall through to return 1 from hw_breakpoint_pending() "unhandled fault" so userspace can make use of this breakpoint. Tested with LKDTM and this command line: echo CFI_FORWARD_PROTO > /sys/kernel/debug/provoke-crash/DIRECT still works as expected.
https://git.kernel.org/stable/c/da64b150e4b7bee615b33ab21f3137c31ec36922
https://git.kernel.org/stable/c/8ed9bff906cf8036531d1559f10e82733a52b41f
https://git.kernel.org/stable/c/314f1a6762b5d51b37784ed7dc701d4c3d893703
https://git.kernel.org/stable/c/22107402c2669b0163d43cc68901a2c4a59fa43a