KCOV to support in AOSP Android kernel-4.4?

[miles....@gmail.com]

Hi,

Is it possible for Android kernel-4.4 to support KCOV in AOSP?

(https://android.googlesource.com/kernel/common/+/android-4.4)

Most of the Android devices are not using the latest Linux kernel, which make them difficult to integrate with Syzkaller fuzzing.

Syzkaller is a great fuzzer.

If KCOV is supported in Android kernel-4.4 or even Android kernel-3.18 directly, I think more Android vulnerabilities can be found by Syzkaller.

---

I manually patched my kernel-4.4 with the following three patches:

- kernel: add kcov code coverage: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5c9a8750a6409c63a0f01d51a9024861022f6593

- arm64: allow building with kcov coverage on ARM64: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5e4c7549f7082b06bbba566c68696dbb8d2e5b6b

- kcov-allow-more-fine-grained-coverage-instrumentation: https://patchwork.kernel.org/patch/9131777/

I'm not sure if I miss any "required" patch?

I confirmed the result by https://groups.google.com/forum/#!topic/syzkaller/kbfiUW0ep7A

Seems only these patches can make Syzkaller working fine.

Thanks,

Miles

[Dmitry Vyukov]

+AOSP developers, this is a popular request and we need this
ourselves. We have an internal bug open for this. Can you prioritize
this backporting?

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[Mark Salyzyn]

-miles....@gmail.com

"kcov exposes kernel PCs and control flow to user-space which is insecure. But debugfs should not be mapped as user accessible."

Keep in mind that the Android security update release team would consider

this a high on the vulnerability scale and have required code to be

removed, neutered or deactivated. I notice that in our kernels (4.9)

we do not have a base or recommended action w.r.t. KCOV.

We probably should.

File a bug to Android->Android O & Apps->system cc to android-kernel-team+aosp_reviews@ so this can be prioritized, scoped and/or evaluated. We may Cc: with android-security-bugs@ for their feedback at that point. Please put these concerns in the bug description.

-- Mark

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