From 3c75dc1ed9a32fff16c84f60536ee21ff8e9e19f Mon Sep 17 00:00:00 2001

From: Michal Privoznik <mprivozn@redhat.com>

Date: Thu, 18 Sep 2014 15:17:29 +0200

Subject: [PATCH] virSecuritySELinuxSetTapFDLabel: Temporarily revert to old

 behavior

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)

---

 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 e8c13db..c078cab 100644

--- a/src/security/security_selinux.c

+++ b/src/security/security_selinux.c

@@ -2330,17 +2330,47 @@ 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 *