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misc: Mark memory region APIs as unsafe

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To ensure that struct sizes are the same on 32-bit and 64-bit, various
kernel APIs use __u64 (Rust u64) to represent userspace pointers.
Userspace is expected to cast pointers to __u64 before passing them to
the kernel, and cast kernel-provided __u64 to a pointer before using
them.  However, various safe APIs in Cloud Hypervisor took
caller-provided u64 values and passed them to syscalls that treat them
as userspace addresses.  Therefore, passing bad u64 values would cause
memory disclosure or corruption.  The memory region APIs are one example
of this, so mark them as unsafe.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
This commit is contained in:
Demi Marie Obenour
2025-06-13 14:27:00 -04:00
committed by Rob Bradford
parent 00f0b9e42c
commit fdc19ad85e
12 changed files with 489 additions and 407 deletions
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131
hypervisor/src/mshv/mod.rs
View File

@@ -74,35 +74,10 @@ use crate::arch::aarch64::gic::{Vgic, VgicConfig};
use crate::arch::aarch64::regs;
#[cfg(target_arch = "x86_64")]
use crate::arch::x86::{CpuIdEntry, FpuState, MsrEntry};
use crate::{
CpuState, IoEventAddress, IrqRoutingEntry, MpState, USER_MEMORY_REGION_ADJUSTABLE,
USER_MEMORY_REGION_EXECUTE, USER_MEMORY_REGION_READ, USER_MEMORY_REGION_WRITE,
UserMemoryRegion,
};
use crate::{CpuState, IoEventAddress, IrqRoutingEntry, MpState};
pub const PAGE_SHIFT: usize = 12;
impl From<mshv_user_mem_region> for UserMemoryRegion {
fn from(region: mshv_user_mem_region) -> Self {
let mut flags: u32 = USER_MEMORY_REGION_READ | USER_MEMORY_REGION_ADJUSTABLE;
if region.flags & (1 << MSHV_SET_MEM_BIT_WRITABLE) != 0 {
flags |= USER_MEMORY_REGION_WRITE;
}
if region.flags & (1 << MSHV_SET_MEM_BIT_EXECUTABLE) != 0 {
flags |= USER_MEMORY_REGION_EXECUTE;
}
UserMemoryRegion {
guest_phys_addr: (region.guest_pfn << PAGE_SHIFT as u64)
+ (region.userspace_addr & ((1 << PAGE_SHIFT) - 1)),
memory_size: region.size,
userspace_addr: region.userspace_addr,
flags,
..Default::default()
}
}
}
#[cfg(target_arch = "x86_64")]
impl From<MshvClockData> for ClockData {
fn from(d: MshvClockData) -> Self {
@@ -122,26 +97,6 @@ impl From<ClockData> for MshvClockData {
}
}
impl From<UserMemoryRegion> for mshv_user_mem_region {
fn from(region: UserMemoryRegion) -> Self {
let mut flags: u8 = 0;
if region.flags & USER_MEMORY_REGION_WRITE != 0 {
flags |= 1 << MSHV_SET_MEM_BIT_WRITABLE;
}
if region.flags & USER_MEMORY_REGION_EXECUTE != 0 {
flags |= 1 << MSHV_SET_MEM_BIT_EXECUTABLE;
}
mshv_user_mem_region {
guest_pfn: region.guest_phys_addr >> PAGE_SHIFT,
size: region.memory_size,
userspace_addr: region.userspace_addr,
flags,
..Default::default()
}
}
}
impl From<mshv_ioctls::IoEventAddress> for IoEventAddress {
fn from(a: mshv_ioctls::IoEventAddress) -> Self {
match a {
@@ -1918,8 +1873,36 @@ impl vm::Vm for MshvVm {
}
/// Creates a guest physical memory region.
fn create_user_memory_region(&self, user_memory_region: UserMemoryRegion) -> vm::Result<()> {
let user_memory_region: mshv_user_mem_region = user_memory_region.into();
///
/// # Safety
///
/// `userspace_addr` must point to `memory_size` bytes of memory
/// that will stay mapped until a successful call to
/// `remove_user_memory_region().` Freeing them with `munmap()`
/// before then will cause undefined guest behavior but at least
/// should not cause undefined behavior in the host. In theory,
/// at least.
unsafe fn create_user_memory_region(
&self,
_slot: u32,
guest_phys_addr: u64,
memory_size: u64,
userspace_addr: u64,
readonly: bool,
_log_dirty_pages: bool,
) -> vm::Result<()> {
let mut flags = 1 << MSHV_SET_MEM_BIT_EXECUTABLE;
if !readonly {
flags |= 1 << MSHV_SET_MEM_BIT_WRITABLE;
}
let user_memory_region = mshv_user_mem_region {
flags,
guest_pfn: guest_phys_addr >> PAGE_SHIFT,
size: memory_size,
userspace_addr,
..Default::default()
};
// No matter read only or not we keep track the slots.
// For readonly hypervisor can enable the dirty bits,
// but a VM exit happens before setting the dirty bits
@@ -1938,8 +1921,32 @@ impl vm::Vm for MshvVm {
}
/// Removes a guest physical memory region.
fn remove_user_memory_region(&self, user_memory_region: UserMemoryRegion) -> vm::Result<()> {
let user_memory_region: mshv_user_mem_region = user_memory_region.into();
///
/// # Safety
///
/// `userspace_addr` must point to `memory_size` bytes of memory,
/// and `add_user_memory_region()` must have been successfully called.
unsafe fn remove_user_memory_region(
&self,
_slot: u32,
guest_phys_addr: u64,
memory_size: u64,
userspace_addr: u64,
readonly: bool,
_log_dirty_pages: bool,
) -> vm::Result<()> {
let mut flags = 1 << MSHV_SET_MEM_BIT_EXECUTABLE;
if !readonly {
flags |= 1 << MSHV_SET_MEM_BIT_WRITABLE;
}
let user_memory_region = mshv_user_mem_region {
flags,
guest_pfn: guest_phys_addr >> PAGE_SHIFT,
size: memory_size,
userspace_addr,
..Default::default()
};
// Remove the corresponding entry from "self.dirty_log_slots" if needed
self.dirty_log_slots
.write()
@@ -1952,30 +1959,6 @@ impl vm::Vm for MshvVm {
Ok(())
}
fn make_user_memory_region(
&self,
_slot: u32,
guest_phys_addr: u64,
memory_size: u64,
userspace_addr: u64,
readonly: bool,
_log_dirty_pages: bool,
) -> UserMemoryRegion {
let mut flags = 1 << MSHV_SET_MEM_BIT_EXECUTABLE;
if !readonly {
flags |= 1 << MSHV_SET_MEM_BIT_WRITABLE;
}
mshv_user_mem_region {
flags,
guest_pfn: guest_phys_addr >> PAGE_SHIFT,
size: memory_size,
userspace_addr,
..Default::default()
}
.into()
}
fn create_passthrough_device(&self) -> vm::Result<VfioDeviceFd> {
let mut vfio_dev = mshv_create_device {
type_: MSHV_DEV_TYPE_VFIO,