Re: [PATCH 00/26] Fixing wait, exit, ptrace, exec, and CLONE_THREAD

[Aleksa Sarai]

> Another easy entry point is to see that a multi-threaded setuid won't
> change the credentials on a zombie thread group leader.  Which can allow
> sending signals to a process that the credential change should forbid.
> This is in violation of posix and the semantics we attempt to enforce in
> linux.

I might be completely wrong on this point (and I haven't looked at the 
patches), but I was under the impression that multi-threaded set[ug]id 
was implemented in userspace (by glibc's nptl(7) library that uses RT 
signals internally to get each thread to update their credentials). And 
given that, I wouldn't be surprised (as a user) that zombie threads will 
have stale credentials (glibc isn't running in those threads anymore).

Am I mistaken in that belief?

</off-topic>

--
Aleksa Sarai
Software Engineer (Containers)
SUSE Linux GmbH
https://www.cyphar.com/