fix: use correct ioctl wrapper for create_device

Use `ioctl_with_mut_ref` instead of `ioctl_with_ref` in the `create_device` method as it needs to write to the `kvm_create_device` struct passed to it. This incorrect usage of `ioctl_with_ref` causes newer versions of Rust compiler (1.82 and above) to treat the `kvm_create_device` struct as read-only and bypass following reads from it. This optimization lead to incorrect value being passed to the `File::from_raw_fd` call. Signed-off-by: Egor Lazarchuk <[email protected]>
rust-vmm · Dec 9, 2024 · b42e972 · b42e972
1 parent 4508a0f
commit b42e972
Show file tree

Hide file tree

Showing 2 changed files with 7 additions and 1 deletion.
diff --git a/kvm-ioctls/CHANGELOG.md b/kvm-ioctls/CHANGELOG.md
@@ -7,6 +7,12 @@
 - [[#288](https://github.com/rust-vmm/kvm-ioctls/pull/288)]: Introduce `Cap::GuestMemfd`, `Cap::MemoryAttributes` and 
    `Cap::UserMemory2` capabilities enum variants for use with `VmFd::check_extension`.
 
+### Fixed
+
+- [[#298](https://github.com/rust-vmm/kvm/pull/298)]: Fixed incorrect usage of `ioctl_wit_ref` in the
+  `create_device` method. Replace it with `ioctl_wit_mut_ref` as the passed parameter may be mutated by the
+  ioctl.
+
 ## v0.19.0
 
 ### Added

diff --git a/kvm-ioctls/src/ioctls/vm.rs b/kvm-ioctls/src/ioctls/vm.rs
@@ -1300,7 +1300,7 @@ impl VmFd {
     /// ```
     pub fn create_device(&self, device: &mut kvm_create_device) -> Result<DeviceFd> {
         // SAFETY: Safe because we are calling this with the VM fd and we trust the kernel.
-        let ret = unsafe { ioctl_with_ref(self, KVM_CREATE_DEVICE(), device) };
+        let ret = unsafe { ioctl_with_mut_ref(self, KVM_CREATE_DEVICE(), device) };
         if ret == 0 {
             // SAFETY: We validated the return of the function creating the fd and we trust the
             // kernel.