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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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132
hypervisor/src/kvm/mod.rs
View File

@@ -69,11 +69,7 @@ use crate::ClockData;
use crate::arch::x86::{
CpuIdEntry, FpuState, LapicState, MsrEntry, NUM_IOAPIC_PINS, SpecialRegisters, XsaveState,
};
use crate::{
CpuState, IoEventAddress, IrqRoutingEntry, MpState, StandardRegisters,
USER_MEMORY_REGION_LOG_DIRTY, USER_MEMORY_REGION_READ, USER_MEMORY_REGION_WRITE,
UserMemoryRegion,
};
use crate::{CpuState, IoEventAddress, IrqRoutingEntry, MpState, StandardRegisters};
// aarch64 dependencies
#[cfg(target_arch = "aarch64")]
pub mod aarch64;
@@ -234,51 +230,6 @@ pub struct KvmTdxExitVmcall {
pub out_rdx: u64,
}
impl From<kvm_userspace_memory_region> for UserMemoryRegion {
fn from(region: kvm_userspace_memory_region) -> Self {
let mut flags = USER_MEMORY_REGION_READ;
if region.flags & KVM_MEM_READONLY == 0 {
flags |= USER_MEMORY_REGION_WRITE;
}
if region.flags & KVM_MEM_LOG_DIRTY_PAGES != 0 {
flags |= USER_MEMORY_REGION_LOG_DIRTY;
}
UserMemoryRegion {
slot: region.slot,
guest_phys_addr: region.guest_phys_addr,
memory_size: region.memory_size,
userspace_addr: region.userspace_addr,
flags,
}
}
}
impl From<UserMemoryRegion> for kvm_userspace_memory_region {
fn from(region: UserMemoryRegion) -> Self {
assert!(
region.flags & USER_MEMORY_REGION_READ != 0,
"KVM mapped memory is always readable"
);
let mut flags = 0;
if region.flags & USER_MEMORY_REGION_WRITE == 0 {
flags |= KVM_MEM_READONLY;
}
if region.flags & USER_MEMORY_REGION_LOG_DIRTY != 0 {
flags |= KVM_MEM_LOG_DIRTY_PAGES;
}
kvm_userspace_memory_region {
slot: region.slot,
guest_phys_addr: region.guest_phys_addr,
memory_size: region.memory_size,
userspace_addr: region.userspace_addr,
flags,
}
}
}
impl From<kvm_mp_state> for MpState {
fn from(s: kvm_mp_state) -> Self {
MpState::Kvm(s)
@@ -758,10 +709,17 @@ impl vm::Vm for KvmVm {
.map_err(|e| vm::HypervisorVmError::SetGsiRouting(e.into()))
}
/// Creates a guest physical memory region.
///
/// Creates a memory region structure that can be used with {create/remove}_user_memory_region
/// # Safety
///
fn make_user_memory_region(
/// `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,
@@ -769,27 +727,24 @@ impl vm::Vm for KvmVm {
userspace_addr: u64,
readonly: bool,
log_dirty_pages: bool,
) -> UserMemoryRegion {
kvm_userspace_memory_region {
) -> vm::Result<()> {
let mut flags = 0;
if readonly {
flags |= KVM_MEM_READONLY;
}
if log_dirty_pages {
flags |= KVM_MEM_LOG_DIRTY_PAGES;
}
const _: () = assert!(core::mem::size_of::<usize>() <= core::mem::size_of::<u64>());
let mut region = kvm_userspace_memory_region {
slot,
guest_phys_addr,
memory_size,
userspace_addr,
flags: if readonly { KVM_MEM_READONLY } else { 0 }
| if log_dirty_pages {
KVM_MEM_LOG_DIRTY_PAGES
} else {
0
},
}
.into()
}
///
/// Creates a guest physical memory region.
///
fn create_user_memory_region(&self, user_memory_region: UserMemoryRegion) -> vm::Result<()> {
let mut region: kvm_userspace_memory_region = user_memory_region.into();
flags,
};
if (region.flags & KVM_MEM_LOG_DIRTY_PAGES) != 0 {
if (region.flags & KVM_MEM_READONLY) != 0 {
@@ -814,7 +769,7 @@ impl vm::Vm for KvmVm {
region.flags = 0;
}
// SAFETY: Safe because guest regions are guaranteed not to overlap.
// SAFETY: Safe because caller promised this is safe.
unsafe {
self.fd
.set_user_memory_region(region)
@@ -822,18 +777,45 @@ impl vm::Vm for KvmVm {
}
}
///
/// Removes a guest physical memory region.
///
fn remove_user_memory_region(&self, user_memory_region: UserMemoryRegion) -> vm::Result<()> {
let mut region: kvm_userspace_memory_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 = 0;
if readonly {
flags |= KVM_MEM_READONLY;
}
if log_dirty_pages {
flags |= KVM_MEM_LOG_DIRTY_PAGES;
}
const _: () = assert!(core::mem::size_of::<usize>() <= core::mem::size_of::<u64>());
let mut region = kvm_userspace_memory_region {
slot,
guest_phys_addr,
memory_size,
userspace_addr,
flags,
};
// Remove the corresponding entry from "self.dirty_log_slots" if needed
self.dirty_log_slots.write().unwrap().remove(&region.slot);
// Setting the size to 0 means "remove"
region.memory_size = 0;
// SAFETY: Safe because guest regions are guaranteed not to overlap.
// SAFETY: Safe because caller promised this is safe.
unsafe {
self.fd
.set_user_memory_region(region)
@@ -1211,7 +1193,7 @@ impl hypervisor::Hypervisor for KvmHypervisor {
vm_type = KVM_X86_SW_PROTECTED_VM.into();
} else {
vm_type = KVM_X86_DEFAULT_VM.into();
};
}
loop {
match self.kvm.create_vm_with_type(vm_type) {