linux-kernel - Re: [PATCH v2 0/2] setgid hardening

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Date:   Tue, 31 Jan 2017 16:49:37 +1300
From:   Michael Kerrisk <mtk.manpages@...il.com>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     security@...nel.org, Konstantin Khlebnikov <koct9i@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Kees Cook <keescook@...omium.org>, Willy Tarreau <w@....eu>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        yalin wang <yalin.wang2010@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jan Kara <jack@...e.cz>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        Frank Filz <ffilzlnx@...dspring.com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] setgid hardening

[CC += linux-api@]

Andy, this is an API change!

On Sat, Jan 28, 2017 at 3:49 PM, Andy Lutomirski <luto@...nel.org> wrote:
> The kernel has some dangerous behavior involving the creation and
> modification of setgid executables.  These issues aren't kernel
> security bugs per se, but they have been used to turn various
> filesystem permission oddities into reliably privilege escalation
> exploits.
>
> See http://www.halfdog.net/Security/2015/SetgidDirectoryPrivilegeEscalation/
> for a nice writeup.
>
> Let's fix them for real.
>
> Changes from v1:
>  - Fix uninitialized variable issue (Willy, Ben)
>  - Also check current creds in should_remove_suid() (Ben)
>
> Andy Lutomirski (2):
>   fs: Check f_cred as well as of current's creds in should_remove_suid()
>   fs: Harden against open(..., O_CREAT, 02777) in a setgid directory
>
>  fs/inode.c         | 61 ++++++++++++++++++++++++++++++++++++++++++++++--------
>  fs/internal.h      |  2 +-
>  fs/ocfs2/file.c    |  4 ++--
>  fs/open.c          |  2 +-
>  include/linux/fs.h |  2 +-
>  5 files changed, 57 insertions(+), 14 deletions(-)
>
> --
> 2.9.3
>
> --
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-- 
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/