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.
