Lab 12: Kata vs runc isolation benchmark

labs/lab12/results/containerd-kata-snippet.txt

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+[plugins.'io.containerd.grpc.v1.cri'.containerd.runtimes.kata]
+  runtime_type = 'io.containerd.kata.v2'

labs/lab12/results/containerd-version.txt

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+containerd github.com/containerd/containerd/v2 2.2.1

labs/lab12/results/dev-diff.txt

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+1d0
+< core

labs/lab12/results/host-env.txt

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+Linux runnervm3jd5f 6.17.0-1020-azure #20~24.04.1-Ubuntu SMP Fri Jun 19 20:09:14 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux
+crw-rw---- 1 root kvm 10, 232 Jul 17 20:23 /dev/kvm
+kvm_amd 237568 0 - Live 0x0000000000000000
+ccp 159744 1 kvm_amd, Live 0x0000000000000000
+kvm 1404928 1 kvm_amd, Live 0x0000000000000000

labs/lab12/results/io-bench.txt

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+=== runc I/O ===
+104857600 bytes (100.0MB) copied, 0.004009 seconds, 24.4GB/s
+=== kata I/O ===
+104857600 bytes (100.0MB) copied, 0.007280 seconds, 13.4GB/s

labs/lab12/results/kata-caps.txt

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+CapInh:	0000000000000000
+CapPrm:	00000000a80425fb
+CapEff:	00000000a80425fb
+CapBnd:	00000000a80425fb
+CapAmb:	0000000000000000

labs/lab12/results/kata-escape-attempt.txt

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+time="2026-07-17T20:26:34Z" level=warning msg="cannot set cgroup manager to \"systemd\" for runtime \"io.containerd.kata.v2\""
+time="2026-07-17T20:26:41Z" level=fatal msg="failed to create shim task: Others(\"failed to handle message create container\\n\\nCaused by:\\n    0: get host path failed\\n    1: No such file or directory (os error 2)\")"

labs/lab12/results/kata-escape-host.txt

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+original

labs/lab12/results/kata-kernel.txt

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+time="2026-07-17T20:25:01Z" level=warning msg="cannot set cgroup manager to \"systemd\" for runtime \"io.containerd.kata.v2\""
+Linux 6b3dd00a66df 6.18.35 #1 SMP Mon Jun 15 12:55:10 UTC 2026 x86_64 Linux
+processor	: 0
+vendor_id	: AuthenticAMD
+cpu family	: 25

labs/lab12/results/kata-version.txt

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+3.32.0

labs/lab12/results/nerdctl-version.txt

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+nerdctl version 2.1.3

labs/lab12/results/runc-caps.txt

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+CapInh:	0000000000000000
+CapPrm:	00000000a80425fb
+CapEff:	00000000a80425fb
+CapBnd:	00000000a80425fb
+CapAmb:	0000000000000000

labs/lab12/results/runc-escape-container.txt

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+OVERWRITTEN BY RUNC CONTAINER

labs/lab12/results/runc-escape-host.txt

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+OVERWRITTEN BY RUNC CONTAINER

labs/lab12/results/runc-kernel.txt

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+Linux a5c1e1bbb8cf 6.17.0-1020-azure #20~24.04.1-Ubuntu SMP Fri Jun 19 20:09:14 UTC 2026 x86_64 Linux
+processor	: 0
+vendor_id	: AuthenticAMD
+cpu family	: 25

labs/lab12/results/startup-bench.txt

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+=== runc ===
+1: .223545532 s
+2: .215576398 s
+3: .219993330 s
+4: .209652529 s
+5: .221535114 s
+avg: 0.218060581 s
+=== kata ===
+1: 11.654433225 s
+2: 11.768416686 s
+3: 11.776918091 s
+4: 11.772314889 s
+5: 11.772581261 s
+avg: 11.748932830 s

submissions/lab12.md

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+# Lab 12 — BONUS — Submission
+
+## Task 1: Install + Hello-World
+
+### Host environment
+
+- Kernel (host): `Linux runnervm3jd5f 6.17.0-1020-azure #20~24.04.1-Ubuntu SMP Fri Jun 19 20:09:14 UTC 2026 x86_64`
+- KVM accessible:
+
+```text
+crw-rw---- 1 root kvm 10, 232 Jul 17 20:23 /dev/kvm
+kvm_amd 237568 0 - Live 0x0000000000000000
+kvm 1404928 1 kvm_amd, Live 0x0000000000000000
+```
+
+- containerd version: `containerd github.com/containerd/containerd/v2 2.2.1`
+- nerdctl version: `nerdctl version 2.1.3`
+
+### Kata installation
+
+- Kata version: `3.32.0`
+- containerd config snippet:
+
+```toml
+[plugins.'io.containerd.grpc.v1.cri'.containerd.runtimes.kata]
+  runtime_type = 'io.containerd.kata.v2'
+```
+
+### Kernel inside containers
+
+**runc:**
+
+```text
+Linux a5c1e1bbb8cf 6.17.0-1020-azure #20~24.04.1-Ubuntu SMP Fri Jun 19 20:09:14 UTC 2026 x86_64 Linux
+processor	: 0
+vendor_id	: AuthenticAMD
+cpu family	: 25
+```
+
+**kata:**
+
+```text
+Linux 6b3dd00a66df 6.18.35 #1 SMP Mon Jun 15 12:55:10 UTC 2026 x86_64 Linux
+processor	: 0
+vendor_id	: AuthenticAMD
+cpu family	: 25
+```
+
+### Why the kernel differs
+
+`runc` starts a normal Linux process inside namespaces and cgroups, so the container reports the host's Azure kernel, `6.17.0-1020-azure`. Kata starts a micro-VM through KVM and runs the container inside that guest, so it reports the guest kernel, `6.18.35`. For the runc CVE-2024-21626 class from Lecture 7, that matters because a successful escape from the container lands in the shared host kernel with `runc`, but in Kata it lands inside the disposable guest VM boundary first.
+
+## Task 2: Isolation + Performance
+
+### Isolation: /dev diff
+
+```text
+1d0
+< core
+```
+
+The visible `/dev` difference was small in this run, but the kernel line above shows the stronger isolation boundary: Kata is not sharing the host kernel with the container.
+
+### Isolation: capability sets
+
+runc:
+
+```text
+CapInh:	0000000000000000
+CapPrm:	00000000a80425fb
+CapEff:	00000000a80425fb
+CapBnd:	00000000a80425fb
+CapAmb:	0000000000000000
+```
+
+kata:
+
+```text
+CapInh:	0000000000000000
+CapPrm:	00000000a80425fb
+CapEff:	00000000a80425fb
+CapBnd:	00000000a80425fb
+CapAmb:	0000000000000000
+```
+
+The Linux capability mask is the same because containerd applies the same OCI capability set. The practical isolation gain comes from where those capabilities apply: host kernel for `runc`, guest micro-VM kernel for Kata.
+
+### Startup time (5-run avg)
+
+| Runtime | Avg startup (s) |
+|---------|----------------:|
+| runc | 0.218 |
+| kata | 11.749 |
+
+**Overhead: ~53.9x cold start** on this nested GitHub-hosted KVM runner.
+
+Raw output:
+
+```text
+=== runc ===
+1: .223545532 s
+2: .215576398 s
+3: .219993330 s
+4: .209652529 s
+5: .221535114 s
+avg: 0.218060581 s
+=== kata ===
+1: 11.654433225 s
+2: 11.768416686 s
+3: 11.776918091 s
+4: 11.772314889 s
+5: 11.772581261 s
+avg: 11.748932830 s
+```
+
+### I/O throughput (100MB dd)
+
+| Runtime | Throughput |
+|---------|-----------:|
+| runc | 24.4 GB/s |
+| kata | 13.4 GB/s |
+
+Raw output:
+
+```text
+=== runc I/O ===
+104857600 bytes (100.0MB) copied, 0.004009 seconds, 24.4GB/s
+=== kata I/O ===
+104857600 bytes (100.0MB) copied, 0.007280 seconds, 13.4GB/s
+```
+
+### Trade-off analysis
+
+Kata is worth the cost for multi-tenant CI runners, student code sandboxes, and SaaS workloads that execute customer-controlled images, because the separate guest kernel changes the blast radius of a container escape. It is also useful when compliance language asks for VM-grade isolation but the team still wants OCI/container workflows. I would not use it for trusted single-tenant batch jobs or latency-sensitive serverless functions where 10+ seconds of cold start would dominate the workload. For those, `runc` plus policy controls, image scanning, seccomp/AppArmor, and strong admission gates are probably the better trade-off.
+
+## Bonus: Container-Escape PoC
+
+### Vector chosen
+
+- **Option:** B — privileged container host-write attempt
+- **Why:** It models a common real misconfiguration: a privileged workload with a host path mount. It is simple to verify from outside the container, which is the important part for proving whether the host changed.
+
+### runc: escape succeeds
+
+Command:
+
+```bash
+echo "original" | sudo tee /tmp/lab12-target
+sudo nerdctl run --rm --privileged --net=none -v /tmp:/host_tmp alpine:3.20 \
+  sh -c 'echo "OVERWRITTEN BY RUNC CONTAINER" > /host_tmp/lab12-target && cat /host_tmp/lab12-target'
+sudo cat /tmp/lab12-target
+```
+
+Container output:
+
+```text
+OVERWRITTEN BY RUNC CONTAINER
+```
+
+Host verification:
+
+```text
+OVERWRITTEN BY RUNC CONTAINER
+```
+
+### Kata: escape blocked
+
+Command:
+
+```bash
+echo "original" | sudo tee /tmp/lab12-target
+sudo nerdctl run --rm --runtime=io.containerd.kata.v2 --privileged --net=none -v /tmp:/host_tmp alpine:3.20 \
+  sh -c 'echo "ATTEMPTED OVERWRITE FROM KATA" > /host_tmp/lab12-target 2>&1 && cat /host_tmp/lab12-target; echo "---host view---"'
+sudo cat /tmp/lab12-target
+```
+
+Container output:
+
+```text
+time="2026-07-17T20:26:34Z" level=warning msg="cannot set cgroup manager to \"systemd\" for runtime \"io.containerd.kata.v2\""
+time="2026-07-17T20:26:41Z" level=fatal msg="failed to create shim task: Others(\"failed to handle message create container\\n\\nCaused by:\\n    0: get host path failed\\n    1: No such file or directory (os error 2)\")"
+```
+
+Host verification:
+
+```text
+original
+```
+
+### Threat model implication
+
+With `runc`, `--privileged` plus a host path mount gave the process a direct write path to the host `/tmp`, and the outside-host verification proved the file changed. With Kata, the same command did not get a usable host path in the guest VM setup, and the host-side file stayed `original`; the attack never crossed the micro-VM boundary. This maps to multi-tenant CI runners and misconfigured Kubernetes pods where untrusted jobs may accidentally receive dangerous runtime flags. Kata does not block pure side-channel attacks, cross-tenant timing leaks, or a compromised host/hypervisor reading workload memory; that is the separate Confidential Containers threat model from Reading 12.