From 7d1c85df653dc7fd23b7cfc267e4ccce7a0b15a9 Mon Sep 17 00:00:00 2001
Message-Id: <7d1c85df653dc7fd23b7cfc267e4ccce7a0b15a9@dist-git>
From: Michal Privoznik <mprivozn@redhat.com>
Date: Mon, 6 Oct 2014 14:30:54 +0200
Subject: [PATCH] virSecuritySELinuxSetTapFDLabel: Temporarily revert to old
 behavior

RHEL-7: https://bugzilla.redhat.com/show_bug.cgi?id=1095636
Fedora: https://bugzilla.redhat.com/show_bug.cgi?id=1141879

A long time ago I've implemented support for so called multiqueue
net.  The idea was to let guest network traffic be processed by
multiple host CPUs and thus increasing performance. However, this
behavior is enabled by QEMU via special ioctl() iterated over the
all tap FDs passed in by libvirt. Unfortunately, SELinux comes in
and disallows the ioctl() call because the /dev/net/tun has label
system_u:object_r:tun_tap_device_t:s0 and 'attach_queue' ioctl()
is not allowed on tun_tap_device_t type. So after discussion with
a SELinux developer we've decided that the FDs passed to the QEMU
should be labelled with svirt_t type and SELinux policy will
allow the ioctl(). Therefore I've made a patch
(cf976d9dcf4e592261b14f03572) that does exactly this. The patch
was fixed then by a4431931393aeb1ac5893f121151fa3df4fde612 and
b635b7a1af0e64754016d758376f382470bc11e7. However, things are not
that easy - even though the API to label FD is called
(fsetfilecon_raw) the underlying file is labelled too! So
effectively we are mangling /dev/net/tun label. Yes, that broke
dozen of other application from openvpn, or boxes, to qemu
running other domains.

The best solution would be if SELinux provides a way to label an
FD only, which could be then labeled when passed to the qemu.
However that's a long path to go and we should fix this
regression AQAP. So I went to talk to the SELinux developer again
and we agreed on temporary solution that:

1) All the three patches are reverted
2) SELinux temporarily allows 'attach_queue' on the
tun_tap_device_t

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
(cherry picked from commit ba7468dbb13f552a9177d01ea8bad155f9877bc3)
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
---
 src/security/security_selinux.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c
index 7413701..b7c1015 100644
--- a/src/security/security_selinux.c
+++ b/src/security/security_selinux.c
@@ -2345,17 +2345,47 @@ virSecuritySELinuxSetImageFDLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
 }
 
 static int
-virSecuritySELinuxSetTapFDLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
+virSecuritySELinuxSetTapFDLabel(virSecurityManagerPtr mgr,
                                 virDomainDefPtr def,
                                 int fd)
 {
+    struct stat buf;
+    security_context_t fcon = NULL;
     virSecurityLabelDefPtr secdef;
+    char *str = NULL;
+    int rc = -1;
 
     secdef = virDomainDefGetSecurityLabelDef(def, SECURITY_SELINUX_NAME);
     if (!secdef || !secdef->label)
         return 0;
 
-    return virSecuritySELinuxFSetFilecon(fd, secdef->imagelabel);
+    if (fstat(fd, &buf) < 0) {
+        virReportSystemError(errno, _("cannot stat tap fd %d"), fd);
+        goto cleanup;
+    }
+
+    if ((buf.st_mode & S_IFMT) != S_IFCHR) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("tap fd %d is not character device"), fd);
+        goto cleanup;
+    }
+
+    if (getContext(mgr, "/dev/tap.*", buf.st_mode, &fcon) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("cannot lookup default selinux label for tap fd %d"), fd);
+        goto cleanup;
+    }
+
+    if (!(str = virSecuritySELinuxContextAddRange(secdef->label, fcon))) {
+        goto cleanup;
+    } else {
+        rc = virSecuritySELinuxFSetFilecon(fd, str);
+    }
+
+ cleanup:
+    freecon(fcon);
+    VIR_FREE(str);
+    return rc;
 }
 
 static char *
-- 
2.1.2