vmm: replace as <pointer> casts with safer alternatives

`as` casts can change mutability, which quickly leads to undefined
behavior.

Signed-off-by: Julian Schindel <mail@arctic-alpaca.de>

vmm/src/acpi.rs

@@ -1278,7 +1278,7 @@ mod tests {
         // safe to read. Casting to `u8` satisfies alignment requirements.
         let bytes = unsafe {
             std::slice::from_raw_parts(
-                &gi as *const GenericInitiatorAffinity as *const u8,
+                (&raw const gi).cast::<u8>(),
                 std::mem::size_of::<GenericInitiatorAffinity>(),
             )
         };

vmm/src/console_devices.rs

@@ -87,7 +87,7 @@ fn modify_mode<F: FnOnce(&mut termios)>(
     // and we check the return result.
     let mut termios: termios = unsafe { zeroed() };
     // SAFETY: see above
-    let ret = unsafe { tcgetattr(fd, &mut termios as *mut _) };
+    let ret = unsafe { tcgetattr(fd, &raw mut termios) };
     if ret < 0 {
         return vmm_sys_util::errno::errno_result();
     }
@@ -98,7 +98,7 @@ fn modify_mode<F: FnOnce(&mut termios)>(
     f(&mut termios);
     // SAFETY: Safe because the syscall will only read the extent of termios and we check
     // the return result.
-    let ret = unsafe { tcsetattr(fd, TCSANOW, &termios as *const _) };
+    let ret = unsafe { tcsetattr(fd, TCSANOW, &raw const termios) };
     if ret < 0 {
         return vmm_sys_util::errno::errno_result();
     }

vmm/src/cpu.rs

@@ -303,7 +303,7 @@ fn core_scheduling_cookie() -> u64 {
             PR_SCHED_CORE_GET,
             0,
             PR_SCHED_CORE_SCOPE_THREAD,
-            &mut cookie as *mut u64,
+            &raw mut cookie,
         )
     };
     if ret == -1 {
@@ -1187,12 +1187,13 @@ impl CpuManager {
                 .spawn(move || {
                     // Schedule the thread to run on the expected CPU set
                     if let Some(cpuset) = cpuset.as_ref() {
+                        let cpuset: *const libc::cpu_set_t = cpuset;
                         // SAFETY: FFI call with correct arguments
                         let ret = unsafe {
                             libc::sched_setaffinity(
                                 0,
                                 std::mem::size_of::<libc::cpu_set_t>(),
-                                cpuset as *const libc::cpu_set_t,
+                                cpuset,
                             )
                         };
 

vmm/src/device_manager.rs

@@ -4902,7 +4902,7 @@ impl DeviceManager {
                         .remove_userspace_mapping(
                             mapping.addr.raw_value(),
                             mapping.mapping.size(),
-                            mapping.mapping.as_ptr() as _,
+                            mapping.mapping.as_ptr().cast(),
                             mapping.mergeable,
                             mapping.mem_slot,
                         )

vmm/src/memory_manager.rs

@@ -1188,7 +1188,7 @@ impl MemoryManager {
             let n = unsafe {
                 libc::read(
                     uffd_raw_fd,
-                    &mut msg as *mut uffd::UffdMsg as *mut libc::c_void,
+                    (&raw mut msg).cast(),
                     std::mem::size_of::<uffd::UffdMsg>(),
                 )
             };
@@ -1824,7 +1824,7 @@ impl MemoryManager {
         let res = unsafe {
             libc::syscall(
                 libc::SYS_mbind,
-                addr as *mut libc::c_void,
+                addr.cast::<libc::c_void>(),
                 len,
                 mode,
                 nodemask.as_ptr(),
@@ -2002,7 +2002,7 @@ impl MemoryManager {
                         // SAFETY: FFI call with correct arguments
                         let ret = unsafe {
                             let addr = r.as_ptr().add(offset);
-                            libc::madvise(addr as _, pages * page_size, libc::MADV_POPULATE_WRITE)
+                            libc::madvise(addr.cast(), pages * page_size, libc::MADV_POPULATE_WRITE)
                         };
                         if ret != 0 {
                             let e = io::Error::last_os_error();
@@ -2021,7 +2021,7 @@ impl MemoryManager {
 
         if thp && !hugepages {
             // SAFETY: FFI call with correct arguments
-            let ret = unsafe { libc::madvise(region.as_ptr() as _, size, libc::MADV_HUGEPAGE) };
+            let ret = unsafe { libc::madvise(region.as_ptr().cast(), size, libc::MADV_HUGEPAGE) };
             if ret != 0 {
                 let e = io::Error::last_os_error();
                 warn!("Failed to mark pages as THP eligible: {e}");
@@ -2319,7 +2319,7 @@ impl MemoryManager {
         // mmap succeeded.
         let ret = unsafe {
             libc::madvise(
-                userspace_addr as *mut libc::c_void,
+                userspace_addr.cast(),
                 memory_size as libc::size_t,
                 libc::MADV_DONTDUMP,
             )
@@ -2335,7 +2335,7 @@ impl MemoryManager {
             // mmap succeeded.
             let ret = unsafe {
                 libc::madvise(
-                    userspace_addr as *mut libc::c_void,
+                    userspace_addr.cast(),
                     memory_size as libc::size_t,
                     libc::MADV_MERGEABLE,
                 )
@@ -2400,7 +2400,7 @@ impl MemoryManager {
             // previously advised.
             let ret = unsafe {
                 libc::madvise(
-                    userspace_addr as *mut libc::c_void,
+                    userspace_addr.cast(),
                     memory_size as libc::size_t,
                     libc::MADV_UNMERGEABLE,
                 )

vmm/src/vm.rs

@@ -4069,7 +4069,7 @@ pub fn test_vm() {
                 index as u32,
                 region.start_addr().raw_value(),
                 region.len().try_into().unwrap(),
-                region.as_ptr() as _,
+                region.as_ptr().cast(),
                 false,
                 false,
             )