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Commit 6cffb252 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Jiri Slaby
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userns: Check euid no fsuid when establishing an unprivileged uid mapping



commit 80dd00a2 upstream.

setresuid allows the euid to be set to any of uid, euid, suid, and
fsuid.  Therefor it is safe to allow an unprivileged user to map
their euid and use CAP_SETUID privileged with exactly that uid,
as no new credentials can be obtained.

I can not find a combination of existing system calls that allows setting
uid, euid, suid, and fsuid from the fsuid making the previous use
of fsuid for allowing unprivileged mappings a bug.

This is part of a fix for CVE-2014-8989.

Reviewed-by: default avatarAndy Lutomirski <luto@amacapital.net>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
parent c75f0d0b
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