Contributing to Linux Kernel security
an idea by pperego
Updated 10 months ago. 3 hacker ♥️. 3 followers. Has no hacker: grab it!

Description

A couple of weeks ago, I found this blog post by Gustavo Silva, a Linux Kernel contributor.

I always strived to start again into hacking the Linux Kernel, so I asked Coverity scan dashboard access and I want to contribute to Linux Kernel by fixing some minor issues.

I want also to create a Linux Kernel fuzzing lab using qemu and syzkaller

Goals

  1. Fix at least 2 security bugs
  2. Create the fuzzing lab and having it running

The story so far

  • Day 1: setting up a virtual machine for kernel development using Tumbleweed. Reading a lot of documentation, taking confidence with Coverity dashboard and with procedures to submit a kernel patch
  • Day 2: I read really a lot of documentation and I triaged some findings on Coverity SAST dashboard. I have to confirm that SAST tool are great false positives generator, even for low hanging fruits.
  • Day 3: Working on trivial changes after I read this blog post: https://www.toblux.com/posts/2024/02/linux-kernel-patches.html. I have to take confidence with the patch preparation and submit process yet.
    • First trivial patch sent: using strtruefalse() macro instead of hard-coded strings in a staging driver for a lcd display
    • Fix for a dereference before null check issue discovered by Coverity (CID 1601566) https://scan7.scan.coverity.com/#/project-view/52110/11354?selectedIssue=1601566
  • Day 4: Triaging more issues found by Coverity.
    • The patch for CID 1601566 was refused. The check against the NULL pointer was pointless so I prepared a version 2 of the patch removing the check.
    • Fixed another dereference before NULL check in iwlmvmparsewowlaninfo_notif() routine (CID 1601547). This one was already submitted by another kernel hacker :(
  • Day 5: Wrapping up. I had to do some minor rework on patch for CID 1601566. I found a stalker bothering me in private emails and people I interacted with me, advised he is a well known bothering person. Markus Elfring for the record.

  • Wrapping up: being back doing kernel hacking is amazing and I don't want to stop it. My battery pack is completely drained but changing the scope gave me a great twist and I really want to feel this energy not doing a single task for months.

    I failed in setting up a fuzzing lab but I was too optimistic for the patch submission process.

The patches

1 2

First result

The patch is included in the Linux Kernel.

Resources

The dashboard

The serie of blog posts by Gustavo Silva inspiring this project.

An email with some quick "where to start" instructions The patchset philosophy

No Hackers yet

Join this project

Looking for hackers with the skills:

linux kernel security

This project is part of:

Hack Week 24

Activity

  • 11 months ago: andreabenini liked this project.
  • 12 months ago: wfrisch liked this project.
  • 12 months ago: dbenini liked this project.
  • 12 months ago: pperego added keyword "linux" to this project.
  • 12 months ago: pperego added keyword "kernel" to this project.
  • 12 months ago: pperego added keyword "security" to this project.
  • 12 months ago: pperego originated this project.


    • Comments

    Be the first to comment!

    Similar Projects

    pudc - A PID 1 process that barks to the internet by mssola

    Description

    As a fun exercise in order to dig deeper into the Linux kernel, its interfaces, the RISC-V architecture, and all the dragons in between; I'm building a blog site cooked like this:

    • The backend is written in a mixture of C and RISC-V assembly.
    • The backend is actually PID1 (for real, not within a container).
    • We poll and parse incoming HTTP requests ourselves.
    • The frontend is a mere HTML page with htmx.

    The project is meant to be Linux-specific, so I'm going to use io_uring, pidfs, namespaces, and Linux-specific features in order to drive all of this.

    I'm open for suggestions and so on, but this is meant to be a solo project, as this is more of a learning exercise for me than anything else.

    Goals

    • Have a better understanding of different Linux features from user space down to the kernel internals.
    • Most importantly: have fun.

    Resources

    pudc - A PID 1 process that barks to the internet by mssola

    Description

    As a fun exercise in order to dig deeper into the Linux kernel, its interfaces, the RISC-V architecture, and all the dragons in between; I'm building a blog site cooked like this:

    • The backend is written in a mixture of C and RISC-V assembly.
    • The backend is actually PID1 (for real, not within a container).
    • We poll and parse incoming HTTP requests ourselves.
    • The frontend is a mere HTML page with htmx.

    The project is meant to be Linux-specific, so I'm going to use io_uring, pidfs, namespaces, and Linux-specific features in order to drive all of this.

    I'm open for suggestions and so on, but this is meant to be a solo project, as this is more of a learning exercise for me than anything else.

    Goals

    • Have a better understanding of different Linux features from user space down to the kernel internals.
    • Most importantly: have fun.

    Resources

    early stage kdump support by mbrugger

    Project Description

    When we experience a early boot crash, we are not able to analyze the kernel dump, as user-space wasn't able to load the crash system. The idea is to make the crash system compiled into the host kernel (think of initramfs) so that we can create a kernel dump really early in the boot process.

    Goal for the Hackweeks

    1. Investigate if this is possible and the implications it would have (done in HW21)
    2. Hack up a PoC (done in HW22 and HW23)
    3. Prepare RFC series (giving it's only one week, we are entering wishful thinking territory here).

    update HW23

    • I was able to include the crash kernel into the kernel Image.
    • I'll need to find a way to load that from init/main.c:start_kernel() probably after kcsan_init()
    • I workaround for a smoke test was to hack kexec_file_load() systemcall which has two problems:
      1. My initramfs in the porduction kernel does not have a new enough kexec version, that's not a blocker but where the week ended
      2. As the crash kernel is part of init.data it will be already stale once I can call kexec_file_load() from user-space.

    The solution is probably to rewrite the POC so that the invocation can be done from init.text (that's my theory) but I'm not sure if I can reuse the kexec infrastructure in the kernel from there, which I rely on heavily.

    update HW24

    • Day1
      • rebased on v6.12 with no problems others then me breaking the config
      • setting up a new compilation and qemu/virtme env
      • getting desperate as nothing works that used to work
    • Day 2
      • getting to call the invocation of loading the early kernel from __init after kcsan_init()

    • Day 3

      • fix problem of memdup not being able to alloc so much memory... use 64K page sizes for now
      • code refactoring
      • I'm now able to load the crash kernel
      • When using virtme I can boot into the crash kernel, also it doesn't boot completely (major milestone!), crash in elfcorehdr_read_notes()

    • Day 4

      • crash systems crashes (no pun intended) in copy_old_mempage() link; will need to understand elfcorehdr...
      • call path vmcore_init() -> parse_crash_elf_headers() -> elfcorehdr_read() -> read_from_oldmem() -> copy_oldmem_page() -> copy_to_iter()

    • Day 5

      • hacking arch/arm64/kernel/crash_dump.c:copy_old_mempage() to see if crash system really starts. It does.
      • fun fact: retested with more reserved memory and with UEFI FW, host kernel crashes in init but directly starts the crash kernel, so it works (somehow) \o/

    • TODOs

      • fix elfcorehdr so that we actually can make use of all this...
      • test where in the boot __init() chain we can/should call kexec_early_dump()