virtio-devices: 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>

virtio-devices/src/balloon.rs

@@ -185,7 +185,7 @@ impl BalloonEpollHandler {
         let res =
             // SAFETY: FFI call with valid arguments, guaranteed by VolatileSlice
             unsafe {
-                libc::madvise(slice.ptr_guard_mut().as_ptr() as *mut libc::c_void,
+                libc::madvise(slice.ptr_guard_mut().as_ptr().cast(),
                 range_len as libc::size_t, advice) };
         if res != 0 {
             return Err(Error::MadviseFail(io::Error::last_os_error()));

virtio-devices/src/block.rs

@@ -605,13 +605,10 @@ Setting device status to 'NEEDS_RESET' and stopping processing queues until rese
 
         // 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,
-                )
+                libc::sched_setaffinity(0, std::mem::size_of::<libc::cpu_set_t>(), cpuset)
             };
 
             if ret != 0 {
@@ -1070,7 +1067,7 @@ impl VirtioDevice for Block {
     fn write_config(&mut self, offset: u64, data: &[u8]) {
         // The "writeback" field is the only mutable field
         let writeback_offset =
-            (&self.config.writeback as *const _ as u64) - (&self.config as *const _ as u64);
+            (&raw const self.config.writeback as u64) - (&raw const self.config as u64);
         if offset != writeback_offset || data.len() != std::mem::size_of_val(&self.config.writeback)
         {
             error!(

virtio-devices/src/iommu.rs

@@ -1081,7 +1081,7 @@ impl VirtioDevice for Iommu {
     fn write_config(&mut self, offset: u64, data: &[u8]) {
         // The "bypass" field is the only mutable field
         let bypass_offset =
-            (&self.config.bypass as *const _ as u64) - (&self.config as *const _ as u64);
+            (&raw const self.config.bypass as u64) - (&raw const self.config as u64);
         if offset != bypass_offset || data.len() != std::mem::size_of_val(&self.config.bypass) {
             error!(
                 "Attempt to write to read-only field: offset {:x} length {}",

virtio-devices/src/mem.rs

@@ -480,7 +480,7 @@ impl MemEpollHandler {
             // alone is not past the end.
             let res = unsafe {
                 libc::madvise(
-                    self.region.as_ptr().offset(offset as isize) as *mut libc::c_void,
+                    self.region.as_ptr().offset(offset as isize).cast(),
                     size as libc::size_t,
                     libc::MADV_DONTNEED,
                 )

virtio-devices/src/vhost_user/blk.rs

@@ -233,7 +233,7 @@ impl VirtioDevice for Blk {
     fn write_config(&mut self, offset: u64, data: &[u8]) {
         // The "writeback" field is the only mutable field
         let writeback_offset =
-            (&self.config.writeback as *const _ as u64) - (&self.config as *const _ as u64);
+            (&raw const self.config.writeback as u64) - (&raw const self.config as u64);
         if offset != writeback_offset || data.len() != std::mem::size_of_val(&self.config.writeback)
         {
             error!(

virtio-devices/src/vhost_user/vu_common_ctrl.rs

@@ -687,7 +687,7 @@ impl VhostUserHandle {
             // SAFETY: region is of size len
             let bitmap: &[u64] = unsafe {
                 // Cast the pointer to u64
-                let ptr = region.as_ptr() as *const u64;
+                let ptr = region.as_ptr().cast();
                 std::slice::from_raw_parts(ptr, len)
             };
             Ok(MemoryRangeTable::from_dirty_bitmap(

virtio-devices/src/vsock/packet.rs

@@ -396,7 +396,7 @@ impl VsockPacket {
             PacketBuffer::Borrowed { ptr, len } => {
                 // SAFETY: bound checks have already been performed when creating the packet
                 // from the virtq descriptor.
-                Some(unsafe { std::slice::from_raw_parts(*ptr as *const u8, *len) })
+                Some(unsafe { std::slice::from_raw_parts((*ptr).cast(), *len) })
             }
         }
     }