On Mon, Jan 30, 2017 at 7:49 PM, Michael Kerrisk [off-list ref] 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 [off-list ref] wrote:

quoted

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

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