On Fri, Jan 13, 2017 at 11:12:43AM +0100, Michal Privoznik wrote:
When creating new /dev/* for qemu, we do chown() and copy ACLs to
create the exact copy from the original /dev. I though that
copying SELinux labels is not necessary as SELinux will chose the
sane defaults. Surprisingly, it does not leaving namespace with
the following labels:

crw-rw-rw-. root root system_u:object_r:tmpfs_t:s0     random
crw-------. root root system_u:object_r:tmpfs_t:s0     rtc0
drwxrwxrwt. root root system_u:object_r:tmpfs_t:s0     shm
crw-rw-rw-. root root system_u:object_r:tmpfs_t:s0     urandom

As a result, domain is unable to start:

error: internal error: process exited while connecting to monitor: Error in 
GnuTLS initialization: Failed to acquire random data.
qemu-kvm: cannot initialize crypto: Unable to initialize GNUTLS library: Failed 
to acquire random data.

The solution is to copy the SELinux labels as well.

Reported-by: Andrea Bolognani <abolo...@redhat.com>
Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
---
src/qemu/qemu_domain.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 61 insertions(+)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 1399dee0d..a29866673 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -63,6 +63,9 @@
#if defined(HAVE_SYS_MOUNT_H)
# include <sys/mount.h>
#endif
+#ifdef WITH_SELINUX
+# include <selinux/selinux.h>
+#endif

#include <libxml/xpathInternals.h>

@@ -6958,6 +6961,9 @@ qemuDomainCreateDevice(const char *device,
    char *canonDevicePath = NULL;
    struct stat sb;
    int ret = -1;
+#ifdef WITH_SELINUX
+    char *tcon = NULL;
+#endif

    if (virFileResolveAllLinks(device, &canonDevicePath) < 0) {
        if (errno == ENOENT && allow_noent) {
@@ -7023,10 +7029,34 @@ qemuDomainCreateDevice(const char *device,
        goto cleanup;
    }

+#ifdef WITH_SELINUX
+    if (getfilecon_raw(canonDevicePath, &tcon) < 0 &&
+        (errno != ENOTSUP && errno != ENODATA)) {
+        virReportSystemError(errno,
+                             _("Unable to get SELinux label on %s"), 
canonDevicePath);
+        goto cleanup;
+    }
+
+    if (tcon &&
+        setfilecon_raw(devicePath, (VIR_SELINUX_CTX_CONST char *) tcon) < 0) {
+        VIR_WARNINGS_NO_WLOGICALOP_EQUAL_EXPR
+        if (errno != EOPNOTSUPP && errno != ENOTSUP) {
+        VIR_WARNINGS_RESET
+            virReportSystemError(errno,
+                                 _("Unable to set SELinux label on %s"),
+                                 devicePath);
+            goto cleanup;
+        }
+    }
+#endif
+

I think, instead of all the ifdefs, this should be a security driver API
instead of being hardcoded in places.  That way it will be processed
properly by all the security drivers.

For the purpose of this release, let's say I noticed this patch right
after the release and hence didn't have time to NACK it properly on
time.

Martin

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