Merge remote-tracking branch 'remotes/gkurz/tags/fixes-for-2.9' into staging

Merge remote-tracking branch 'remotes/gkurz/tags/fixes-for-2.9' into staging

Fixes issues that got merged with the latest pull request:
- missing O_NOFOLLOW flag for CVE-2016-960
- build break with older glibc that don't have O_PATH and AT_EMPTY_PATH
- various bugs reported by Coverity

# gpg: Signature made Mon 06 Mar 2017 17:51:29 GMT
# gpg:                using DSA key 0x02FC3AEB0101DBC2
# gpg: Good signature from "Greg Kurz <groug@kaod.org>"
# gpg:                 aka "Greg Kurz <groug@free.fr>"
# gpg:                 aka "Greg Kurz <gkurz@linux.vnet.ibm.com>"
# gpg:                 aka "Gregory Kurz (Groug) <groug@free.fr>"
# gpg:                 aka "[jpeg image of size 3330]"
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 2BD4 3B44 535E C0A7 9894  DBA2 02FC 3AEB 0101 DBC2

* remotes/gkurz/tags/fixes-for-2.9:
  9pfs: fix vulnerability in openat_dir() and local_unlinkat_common()
  9pfs: fix O_PATH build break with older glibc versions
  9pfs: don't use AT_EMPTY_PATH in local_set_cred_passthrough()
  9pfs: fail local_statfs() earlier
  9pfs: fix fd leak in local_opendir()
  9pfs: fix bogus fd check in local_remove()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>