{"record":{"id":"3427ff4b33ec7037","repo":"firecracker-microvm/firecracker","slug":"cannot-create-cstring-from-cmdline-string","errorCode":null,"errorMessage":"Cannot create cstring from cmdline string","messagePattern":"Cannot create cstring from cmdline string","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"src/vmm/src/arch/x86_64/mod.rs","lineNumber":262,"sourceCode":"    entry_point: EntryPoint,\n    initrd: &Option<InitrdConfig>,\n    boot_cmdline: Cmdline,\n) -> Result<(), ConfigurationError> {\n    configure_vcpus_for_boot(\n        kvm,\n        vcpus,\n        machine_config,\n        cpu_template,\n        vm.guest_memory(),\n        entry_point,\n    )?;\n\n    // Write the kernel command line to guest memory. This is x86_64 specific, since on\n    // aarch64 the command line will be specified through the FDT.\n    let cmdline_size = boot_cmdline\n        .as_cstring()\n        .map(|cmdline_cstring| cmdline_cstring.as_bytes_with_nul().len())\n        .expect(\"Cannot create cstring from cmdline string\");\n\n    load_cmdline(\n        vm.guest_memory(),\n        GuestAddress(crate::arch::x86_64::layout::CMDLINE_START),\n        &boot_cmdline,\n    )\n    .map_err(ConfigurationError::LoadCommandline)?;\n\n    // Note that this puts the mptable at the last 1k of Linux's 640k base RAM\n    mptable::setup_mptable(\n        vm.guest_memory(),\n        &mut vm.resource_allocator(),\n        machine_config.vcpu_count,\n    )\n    .map_err(ConfigurationError::MpTableSetup)?;\n\n    match entry_point.protocol {\n        BootProtocol::PvhBoot => {","sourceCodeStart":244,"sourceCodeEnd":280,"githubUrl":"https://github.com/firecracker-microvm/firecracker/blob/81b38b9dad6056d7a48073e95ac5a9aed51cb2ab/src/vmm/src/arch/x86_64/mod.rs#L244-L280","documentation":"Error \"Cannot create cstring from cmdline string\" thrown in firecracker-microvm/firecracker.","triggerScenarios":"Thrown at src/vmm/src/arch/x86_64/mod.rs:216 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Remove NUL bytes from the kernel command-line string; CString rejects interior NULs.","Validate the boot arguments passed via the API or config for embedded NUL characters."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"81b38b9dad6056d7a48073e95ac5a9aed51cb2ab","analyzedAt":"2026-08-19T05:27:02.517Z","contentChangedAt":"2026-08-19T05:27:02.517Z","schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}