Dragonball: update linux_loader to 0.6.0

Since linux-loader 0.4.0 and 0.5.0 is yanked due to null terminator bug,
we need to update linux-loader to 0.6.0.

And as_str() function should also be changed.

fixes: #5253

Signed-off-by: Chao Wu <chaowu@linux.alibaba.com>

src/dragonball/Cargo.toml

@@ -26,7 +26,7 @@ kvm-bindings = "0.5.0"
 kvm-ioctls = "0.11.0"
 lazy_static = "1.2"
 libc = "0.2.39"
-linux-loader = "0.5.0"
+linux-loader = "0.6.0"
 log = "0.4.14"
 nix = "0.24.2"
 seccompiler = "0.2.0"

src/dragonball/src/device_manager/blk_dev_mgr.rs

@@ -577,7 +577,13 @@ impl BlockDeviceMgr {
     ) -> std::result::Result<(), DeviceMgrError> {
         // Respect user configuration if kernel_cmdline contains "root=",
         // special attention for the case when kernel command line starting with "root=xxx"
-        let old_kernel_cmdline = format!(" {}", kernel_config.kernel_cmdline().as_str());
+        let old_kernel_cmdline = format!(
+            " {:?}",
+            kernel_config
+                .kernel_cmdline()
+                .as_cstring()
+                .map_err(DeviceMgrError::Cmdline)?
+        );
         if !old_kernel_cmdline.contains(" root=") && self.has_root_block {
             let cmdline = kernel_config.kernel_cmdline_mut();
             if let Some(ref uuid) = self.part_uuid {

src/dragonball/src/error.rs

@@ -127,6 +127,10 @@ pub enum StartMicroVmError {
     #[error("failure while configuring guest kernel commandline: {0}")]
     LoadCommandline(#[source] linux_loader::loader::Error),
 
+    /// Cannot process command line string.
+    #[error("failure while processing guest kernel commandline: {0}.")]
+    ProcessCommandlne(#[source] linux_loader::cmdline::Error),
+
     /// The device manager was not configured.
     #[error("the device manager failed to manage devices: {0}")]
     DeviceManager(#[source] device_manager::DeviceMgrError),

src/dragonball/src/vm/x86_64.rs

@@ -217,11 +217,17 @@ impl Vm {
         linux_loader::loader::load_cmdline(vm_memory, cmdline_addr, cmdline)
             .map_err(StartMicroVmError::LoadCommandline)?;
 
+        let cmdline_size = cmdline
+            .as_cstring()
+            .map_err(StartMicroVmError::ProcessCommandlne)?
+            .as_bytes_with_nul()
+            .len();
+
         configure_system(
             vm_memory,
             self.address_space.address_space(),
             cmdline_addr,
-            cmdline.as_str().len() + 1,
+            cmdline_size,
             &initrd,
             self.vm_config.vcpu_count,
             self.vm_config.max_vcpu_count,