Re: [libvirt] [PATCH v8 0/7] file descriptor passing using fd sets

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 (7): 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: Prevent detection of /dev/fdset/ as floppy 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 | 46 +++++---- 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 | 294 +++++++++++++++++++++++++++++++++++++++++++++++++++++ monitor.h | 5 + osdep.c | 117 +++++++++++++++++++++ qapi-schema.json | 98 ++++++++++++++++++ qemu-char.c | 12 ++- qemu-common.h | 2 + qemu-tool.c | 20 ++++ qmp-commands.hx | 117 +++++++++++++++++++++ savevm.c | 4 +- 16 files changed, 721 insertions(+), 55 deletions(-)