During LKRG development and testing I’ve found 7 Linux kernel bugs, 4 of them have CVE numbers (however, 1 CVE number covers 2 bugs):

CVE-2021-3411  - Linux kernel: broken KRETPROBES and OPTIMIZER
CVE-2020-27825 - Linux kernel: Use-After-Free in the ftrace ring buffer
                 resizing logic due to a race condition
CVE-2020-25220 - Linux kernel Use-After-Free in backported patch for
                 CVE-2020-14356 (affected kernels: 4.9.x before 4.9.233,
                 4.14.x before 4.14.194, and 4.19.x before 4.19.140)
CVE-2020-14356 - Linux kernel Use-After-Free in cgroup BPF component
                 (affected kernels: since 4.5+ up to 5.7.10)

I’ve also found 2 other issues related to the ftrace UAF bug (CVE-2020-27825):

  • Deadlock issue which was not really addressed and devs said they will take a look and there is not much updates on that.
  • Problem with the code related to hwlatd kernel thread – it is incorrectly synchronizing with launcher / killer of it. You can have WARN in kernels all the time.

CVE-2021-3411 refers to 2 different type of bugs:

  • Broken KRETPROBE (recently reported)
  • Incompatibility of KPROBE optimizer with the latest changes in the linker.

Additionally, I’ve also found a bug with the kernel signal handling in dying process:

CVE-2020-12826 – Linux kernel prior to 5.6.5 does not sufficiently restrict exit signals

However, I don’t remember if I found it during my work related to LKRG so I’m not counting it here (otherwise it would be total 8 bugs while 5 of them would have CVE).

That’s pretty bad stats… However, it might be an interesting story to say during LKRG announcement of the new version. It could be also interesting talk for conference.

Full announcement can be read here:

Best regards,


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