fix(vmm): bound vcpu/memory arithmetic and reject zero resources at deployment

dstack/vmm/src/app.rs

@@ -209,6 +209,7 @@ impl GpuConfig {
 
 /// Round up a value to the nearest multiple of another value.
 /// If the value is already a multiple, it remains unchanged.
+/// Left unchanged if the next multiple overflows, rather than wrapping to a tiny value.
 pub(crate) fn round_up(value: u32, multiple: u32) -> u32 {
     if multiple <= 1 {
         return value;
@@ -219,7 +220,7 @@ pub(crate) fn round_up(value: u32, multiple: u32) -> u32 {
         return value;
     }
 
-    value + (multiple - remainder)
+    value.checked_add(multiple - remainder).unwrap_or(value)
 }
 
 /// Get the NUMA node associated with a PCI device.
@@ -3263,6 +3264,11 @@ mod tests {
         Ok(config)
     }
 
+    #[test]
+    fn round_up_does_not_wrap() {
+        assert_eq!(round_up(u32::MAX, 2), u32::MAX);
+    }
+
     #[test]
     fn effective_vcpu_count_clamps_zero_to_one() {
         assert_eq!(effective_vcpu_count(0, None), 1);

dstack/vmm/src/app/qemu.rs

@@ -896,7 +896,7 @@ impl QemuCommandBuilder<'_> {
             ));
             bus_number += device_count + 1;
         }
-        Ok((smp, memory_gib * 1024))
+        Ok((smp, memory_gib.saturating_mul(1024)))
     }
 
     fn configure_gpus(&self, command: &mut Command) -> Result<()> {

dstack/vmm/src/main_service.rs

@@ -314,6 +314,16 @@ pub fn create_manifest_from_vm_config(
     cvm_config: &crate::config::CvmConfig,
 ) -> Result<Manifest> {
     validate_label(&request.name)?;
+    // Same checks as `validate_resize_request`.
+    if request.vcpu == 0 {
+        bail!("vcpu must be greater than zero");
+    }
+    if request.memory == 0 {
+        bail!("memory must be greater than zero");
+    }
+    if request.disk_size == 0 {
+        bail!("disk_size must be greater than zero");
+    }
 
     let port_map = port_map_from_proto(&request.ports, &cvm_config.port_mapping, &[])?;
     let networks = networks_from_vm_config(&request, cvm_config)?;
@@ -1749,6 +1759,13 @@ mod tests {
         assert!(!err.contains("storage_discard"), "{err}");
     }
 
+    #[test]
+    fn deployment_rejects_zero_resources() {
+        let mut request = test_vm_configuration();
+        request.memory = 0;
+        assert!(create_manifest_from_vm_config(request, &test_cvm_config()).is_err());
+    }
+
     #[test]
     fn resize_request_rejects_empty_zero_and_empty_image_updates() {
         let mut request = ResizeVmRequest {