Re: [libvirt] [Qemu-devel] [PATCH v7 0/6] file descriptor passing using fd sets

On 08/08/2012 11:58 AM, Stefan Hajnoczi wrote: > > On Wed, Aug 8, 2012 at 3:54 PM, Corey Bryant <coreyb(a)linux.vnet.ibm.com&gt; > wrote: >> >> >> >> On 08/08/2012 09:04 AM, Stefan Hajnoczi wrote: >>> >>> >>> On Tue, Aug 7, 2012 at 4:58 PM, Corey Bryant <coreyb(a)linux.vnet.ibm.com&gt; >>> wrote: >>>> >>>> >>>> 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 stored on the same NFS >>>> mount. >>>> >>>> This patch series adds the add-fd, remove-fd, and query-fdsets >>>> QMP monitor commands, which allow file descriptors to be passed >>>> via SCM_RIGHTS, and assigned to specified fd sets. This allows >>>> fd sets to be created per file with fds having, for example, >>>> different access rights. When QEMU needs to reopen a file with >>>> different access rights, it can search for a matching fd in the >>>> fd set. Fd sets also allow for easy tracking of fds per file, >>>> helping to prevent fd leaks. >>>> >>>> Support is also added to the block layer to allow QEMU to dup an >>>> fd from an fdset when the filename is of the /dev/fdset/nnn format, >>>> where nnn is the fd set ID. >>>> >>>> No new SELinux policy is required to prevent open of NFS files >>>> (files with type nfs_t). The virt_use_nfs boolean type simply >>>> needs to be set to false, and open will be prevented (and dup will >>>> be allowed). For example: >>>> >>>> # setsebool virt_use_nfs 0 >>>> # getsebool virt_use_nfs >>>> virt_use_nfs --> off >>>> >>>> Corey Bryant (6): >>>> qemu-char: Add MSG_CMSG_CLOEXEC flag to recvmsg >>>> qapi: Introduce add-fd, remove-fd, query-fdsets >>>> monitor: Clean up fd sets on monitor disconnect >>>> block: Convert open calls to qemu_open >>>> block: Convert close calls to qemu_close >>>> block: Enable qemu_open/close to work with fd sets >>>> >>>> block/raw-posix.c | 42 ++++----- >>>> block/raw-win32.c | 6 +- >>>> block/vdi.c | 5 +- >>>> block/vmdk.c | 25 +++-- >>>> block/vpc.c | 4 +- >>>> block/vvfat.c | 16 ++-- >>>> cutils.c | 5 + >>>> monitor.c | 273 >>>> +++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>> monitor.h | 5 + >>>> osdep.c | 117 +++++++++++++++++++++++ >>>> qapi-schema.json | 110 +++++++++++++++++++++ >>>> qemu-char.c | 12 ++- >>>> qemu-common.h | 2 + >>>> qemu-tool.c | 20 ++++ >>>> qerror.c | 4 + >>>> qerror.h | 3 + >>>> qmp-commands.hx | 131 +++++++++++++++++++++++++ >>>> savevm.c | 4 +- >>>> 18 files changed, 730 insertions(+), 54 deletions(-) >>> >>> >>> >>> Are there tests for this feature? Do you have test scripts used >>> during development? >> >> >> >> Yes I have some C code that I've been using for testing. I can clean it >> up >> and provide it if you'd like. > > > That would be very useful. tests/ has test cases. For the block > layer tests/qemu-iotests/ is especially relevant, that's where a lot > of the test cases go. If you look at test case 030 you'll see how a > Python script interacts with QMP to test image streaming - > unfortunately I think Python doesn't natively support SCM_RIGHTS. But > a test script would be very useful so it can be used as a regression > test in the future. > Sure I'll take a look. Hopefully a C test is ok if I can't use SCM_RIGHTS in Python.