kernel-roulette: play Russian Roulette with the Linux kernel

kernel-roulette is a simple Linux kernel module written in Rust and C that implements a character device driver for a virtual device. When this virtual device is read, there is a chance that the system will crash with a kernel panic ^*.

More importantly, it demonstrates how to build a kernel module with Rust. The rust code uses #![no_std] to disable the standard library, but we can still use the following:

• the core crate
• the alloc crate, which includes data structures such as Vec that use dynamic memory allocation.
• macros like println!() to print to the dmesg buffer.

^*: It actually uses the BUG() macro to show a stack trace in dmesg, which doesn't crash the system but leaves it in a somewhat inconsistent state. If you really want it to panic replace abort() with panic_c() in src/lang.rs:31.

Dependencies

• Linux kernel headers and build-essential (gcc, make, etc.)

• Nightly Rust (install from https://rustup.rs)

• Xargo and rust-src

  Download the Rust library source with rustup component add rust-src

  Install xargo with cargo install xargo

• sudo access

Building

• Run make from the project directory
• Run sudo insmod build/roulette.ko
• Run dmesg | tail -n 10 and verify that the kernel module was loaded. You should see something like:

[   35.735871] IPv6: ADDRCONF(NETDEV_UP): enp4s0: link is not ready
[   39.123353] r8169 0000:04:00.0 enp4s0: link up
[   39.123364] IPv6: ADDRCONF(NETDEV_CHANGE): enp4s0: link becomes ready
[  792.965067] roulette: loading out-of-tree module taints kernel.
[  792.965070] roulette: module license 'unspecified' taints kernel.
[  792.965070] Disabling lock debugging due to kernel taint
[  792.965236] roulette: module verification failed: signature and/or required key missing - tainting kernel
[  792.966321] Registered kernel-roulette with major device number 243
[  792.966322] Run /bin/mknod /dev/kernel-roulette c 243 0
[  793.477624] Panic probability: 10/100

• Follow the instructions in dmesg: in this case you would run sudo /bin/mknod /dev/kernel-roulette c 243 0
• Run cat /dev/kernel-roulette
• Unload the module with sudo rmmod build/roulette.ko

Acknowledgements

• rust.ko
• kmod
• The Linux Kernel Module Programming Guide
• https://elixir.bootlin.com/

License

GPL 3