x86 CVT* series instructions fault

Host environment

  • Operating system: Windows 10 20H2
  • OS/kernel version: WSL2 Ubuntu 20.04.4 LTS (GNU/Linux 5.10.102.1-microsoft-standard-WSL2 x86_64)
  • Architecture: x86
  • QEMU flavor: qemu-x86_64
  • QEMU version: 7.1.90 (v7.2.0-rc0)
  • QEMU command line: qemu-x86_64 -cpu max a.out

Emulated/Virtualized environment

  • Operating system: None
  • OS/kernel version: None
  • Architecture: x86

Description of problem

For example, CVTSD2SS instruction converts SRC[63:0] double precision floating point to DEST[31:0] single precision floating point. Although the CVTSD2SS instruction uses only 8 bytes, if it overlaps page boundary, I think QEMU tries to access over the valid memory and crashes.

Steps to reproduce

  1. Compile this code
void main() {
    mmap(0x555555559000, 0x1000, flag, ~~, 0);
    asm("cvtsd2ss xmm1, qword ptr [0x555555559ff8]");
}
  1. Execute. QEMU crashes but CPU does not.

Additional information

This bug is discovered by research conducted by KAIST SoftSec.