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
- Compile this code
void main() {
mmap(0x555555559000, 0x1000, flag, ~~, 0);
asm("cvtsd2ss xmm1, qword ptr [0x555555559ff8]");
}
- Execute. QEMU crashes but CPU does not.
Additional information
This bug is discovered by research conducted by KAIST SoftSec.