On 19/12/2024 4:14 pm, Sedat Dilek wrote: > Hi, > > Linux v6.12.6 will include XEN CVE fixes from mainline. > > Here, I use Debian/unstable AMD64 and the SLIM LLVM toolchain 19.1.x > from kernel.org. > > What does it mean in ISSUE DESCRIPTION... > > Furthermore, the hypercall page has no provision for Control-flow > Integrity schemes (e.g. kCFI/CET-IBT/FineIBT), and will simply > malfunction in such configurations. > > ...when someone uses Clang-kCFI? The hypercall page has functions of the form: MOV $x, %eax VMCALL / VMMCALL / SYSCALL RET There are no ENDBR instructions, and no prologue/epilogue for hash-based CFI schemes. This is because it's code provided by Xen, not code provided by Linux. The absence of ENDBR instructions will yield #CP when CET-IBT is active, and the absence of hash prologue/epilogue lets the function be used in a type-confused manor that CFI should have caught. ~Andrew
