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From: Andy Lutomirski <luto@amacapital.net>
Date: Mon, 30 Jan 2017 19:56:04 -0800
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Subject: Re: [PATCH v2 0/2] setgid hardening
To: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>,
        "security@kernel.org" <security@kernel.org>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Kees Cook <keescook@chromium.org>, Willy Tarreau <w@1wt.eu>,
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        Andrew Morton <akpm@linux-foundation.org>,
        yalin wang <yalin.wang2010@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jan Kara <jack@suse.cz>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Frank Filz <ffilzlnx@mindspring.com>,
        Linux API <linux-api@vger.kernel.org>
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On Mon, Jan 30, 2017 at 7:49 PM, Michael Kerrisk <mtk.manpages@gmail.com> wrote:
> [CC += linux-api@]
>
> Andy, this is an API change!

Indeed.  I should be ashamed of myself!

>
> On Sat, Jan 28, 2017 at 3:49 PM, Andy Lutomirski <luto@kernel.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/



-- 
Andy Lutomirski
AMA Capital Management, LLC