Conversation
jann@infosec.exchange

Jann Horn

I found a Linux kernel security bug (in AF_UNIX) and decided to write a kernel exploit for it that can go straight from "attacker can run arbitrary native code in a seccomp-sandboxed Chrome renderer" to kernel compromise:
https://googleprojectzero.blogspot.com/2025/08/from-chrome-renderer-code-exec-to-kernel.html

This post includes fun things like:

  • a nice semi-arbitrary read primitive combined with an annoying write primitive
  • slowing down usercopy without FUSE or userfaultfd
  • CONFIG_RANDOMIZE_KSTACK_OFFSET as an exploitation aid
  • a rarely-used kernel feature that Chrome doesn't need but is reachable in the Chrome sandbox
  • sched_getcpu() usable inside Chrome renderers despite getcpu being blocked by seccomp (thanks to vDSO)
1
13
1
brauner@mastodon.social

Christian Brauner 🦊🐺

Reply to @jann@infosec.exchange

@jann The real culprit here is coredumps in a way.

2
0
0
jann@infosec.exchange

Jann Horn

Reply to @brauner@mastodon.social
Edited 1 month ago

@brauner new feature work is one of the best ways to find bugs in existing code, I think :D

0
1
1
jann@infosec.exchange

Jann Horn

Reply to @jmorris

@jmorris @brauner Christian is joking about how I only learned about this feature because I looked at a patch that intended to use MSG_OOB as part of the new core dumping mechanism

0
0
1
About social.kernel.org

Terms of service

  1. Please do not use this service in violation of the Linux Kernel Code of Conduct. Doing so will result in your account suspension with the referral of the matter to the CoC committee.

  2. "Repeating"/"boosting" someone else's status on this platform will be treated as endorsement and will fall under rule #1.

  3. You are encouraged to use this platform to promote your work on the Linux Kernel, but there is no restriction on permitted topics (with the exception of anything covered by #1 above).

  4. There is no requirement to post in English, but it should be considered the primary language of communication on this platform.

Privacy notice

The admins of this service have access to all posted statuses. They aren't looking, but if it's something they shouldn't know about, then you should not post it on this platform.

Please see the Linux Foundation Privacy Policy, which applies to this platform as well.

Getting your own account

If you would like an account on this instance, please check that the following applies to you:

  • You are listed in MAINTAINERS or CREDITS

  • OR: You have a kernel.org account or email address

  • OR: You have a long and established history of involvement with the Linux Kernel

If the above is true and you agree with the Terms of Service and Privacy Notice listed above, please use these instructions to request an account: