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

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