[libvirt] [PATCHv3 3/2] qemu: don't request cgroup ACL access for /dev/net/tun

[Eric Blake]

Since libvirt always passes /dev/net/tun to qemu via fd, we should
never trigger the cases where qemu tries to directly open the
device.  Therefore, it is safer to deny the cgroup device ACL.

* src/qemu/qemu_cgroup.c (defaultDeviceACL): Remove /dev/net/tun.
* src/qemu/qemu.conf (cgroup_device_acl): Reflect this change.
---

Might as well fix this in the process of audit cleanups.  I tested
that I was still able to access the network through a virtio
connection with cgroup ACL enforcing in the host after this change.
And it matches the fact that we did not have a cgroup ACL allow
for /dev/tapN devices (also passed via fd).

 src/qemu/qemu.conf     |    2 +-
 src/qemu/qemu_cgroup.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
index 8c6b996..364f555 100644
--- a/src/qemu/qemu.conf
+++ b/src/qemu/qemu.conf
@@ -182,7 +182,7 @@
 #    "/dev/null", "/dev/full", "/dev/zero",
 #    "/dev/random", "/dev/urandom",
 #    "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
-#    "/dev/rtc", "/dev/hpet", "/dev/net/tun",
+#    "/dev/rtc", "/dev/hpet",
 #]


diff --git a/src/qemu/qemu_cgroup.c b/src/qemu/qemu_cgroup.c
index 9a7d42f..8c3eee3 100644
--- a/src/qemu/qemu_cgroup.c
+++ b/src/qemu/qemu_cgroup.c
@@ -37,7 +37,7 @@ static const char *const defaultDeviceACL[] = {
     "/dev/null", "/dev/full", "/dev/zero",
     "/dev/random", "/dev/urandom",
     "/dev/ptmx", "/dev/kvm", "/dev/kqemu",
-    "/dev/rtc", "/dev/hpet", "/dev/net/tun",
+    "/dev/rtc", "/dev/hpet",
     NULL,
 };
 #define DEVICE_PTY_MAJOR 136
-- 
1.7.4