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[libvirt] [RFC PATCH 0/4] block: file descriptor passing using -filefd and getfd_file



libvirt's sVirt security driver provides SELinux MAC isolation for
Qemu guest processes and their corresponding image files.  In other
words, sVirt uses SELinux to prevent a QEMU process from opening
files that do not belong to it.

sVirt provides this support by labeling guests and resources with
security labels that are stored in file system extended attributes.
Some file systems, such as NFS, do not support the extended
attribute security namespace, and therefore cannot support sVirt
isolation.

A solution to this problem is to provide fd passing support, where
libvirt opens files and passes file descriptors to QEMU.  This,
along with SELinux policy to prevent QEMU from opening files, can
provide image file isolation for NFS files.

This patch series adds the -filefd command-line option and the
getfd_file monitor command.  This will enable libvirt to open a
file and push the corresponding filename and file descriptor to
QEMU.  When QEMU needs to "open" a file, it will first check if the
file descriptor was passed by either of these methods before
attempting to actually open the file.

This series reuses the file_open function that Anthony Liguori
<aliguori us ibm com> created for the most recent fd passing
prototype.  It also reuses the test driver that Stefan
Hajnoczi <stefanha linux vnet ibm com> created for that prototype,
with several modifications.

Corey Bryant (4):
  qemu-options: Add -filefd command line option
  qmp/hmp: Add getfd_file monitor command
  block: Enable QEMU to retrieve passed fd before attempting open
  Example -filefd and getfd_file server

 block.c           |   31 +++++++
 block/raw-posix.c |   20 +++---
 block/raw-win32.c |    4 +-
 block/vdi.c       |    4 +-
 block/vmdk.c      |   21 ++---
 block/vpc.c       |    2 +-
 block/vvfat.c     |    4 +-
 block_int.h       |   12 +++
 hmp-commands.hx   |   17 ++++
 monitor.c         |   70 +++++++++++++++++
 monitor.h         |    3 +
 qemu-config.c     |   17 ++++
 qemu-config.h     |    1 +
 qemu-options.hx   |   17 ++++
 qemu-tool.c       |    5 +
 qmp-commands.hx   |   30 +++++++
 test-fd-passing.c |  224 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 vl.c              |    6 ++
 18 files changed, 459 insertions(+), 29 deletions(-)
 create mode 100644 test-fd-passing.c

-- 
1.7.7.6


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