Re: [PATCH v2 0/2] setgid hardening

[Michael Kerrisk]

[CC += linux-api@]

Andy, this is an API change!

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