fix(vmm): bound the event name a guest reports over the host API

docs/tutorials/vmm-configuration.md

@@ -97,6 +97,7 @@ address = "127.0.0.1:9080"
 reuse = true
 kms_url = "http://127.0.0.1:8081"
 event_buffer_size = 20
+max_event_name_len = 128
 node_name = ""
 image_path = "/var/lib/dstack/images"
 

dstack/vmm/src/app.rs

@@ -1507,6 +1507,10 @@ impl App {
     }
 
     pub(crate) fn vm_event_report(&self, cid: u32, event: &str, body: String) -> Result<()> {
+        if event.len() > self.config.max_event_name_len {
+            error!(cid, "event name too large, skipping");
+            return Ok(());
+        }
         info!(cid, event, "VM event");
         if body.len() > 1024 * 4 {
             error!("Event body too large, skipping");

dstack/vmm/src/config.rs

@@ -658,6 +658,9 @@ pub struct Config {
     /// The buffer size in VMM process for guest events
     pub event_buffer_size: usize,
 
+    /// Maximum length in bytes of a guest-reported event name
+    pub max_event_name_len: usize,
+
     /// CVM configuration
     pub cvm: CvmConfig,
 

dstack/vmm/vmm.toml

@@ -12,6 +12,7 @@ address = "unix:./vmm.sock"
 reuse = true
 kms_url = "http://127.0.0.1:8081"
 event_buffer_size = 20
+max_event_name_len = 128
 node_name = ""
 
 [image]