[libvirt] [RFC PATCH 1/2] LXC: Drop capabilities only if we're not within a user namespace

[Richard Weinberger]

Dropping capabilities within a user namespace makes no sense
because any uid 0 process will regain all caps upon execve().

Signed-off-by: Richard Weinberger <richard at nod.at>
---
 src/lxc/lxc_container.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 958e20d..4f00420 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -1896,6 +1896,15 @@ static int lxcContainerDropCapabilities(bool keepReboot ATTRIBUTE_UNUSED)
     return 0;
 }
 
+static int userns_supported(void)
+{
+    return lxcContainerAvailable(LXC_CONTAINER_FEATURE_USER) == 0;
+}
+
+static int userns_required(virDomainDefPtr def)
+{
+    return def->idmap.uidmap && def->idmap.gidmap;
+}
 
 /**
  * lxcContainerChild:
@@ -1992,7 +2001,7 @@ static int lxcContainerChild(void *data)
     }
 
     /* drop a set of root capabilities */
-    if (lxcContainerDropCapabilities(!!hasReboot) < 0)
+    if (!userns_required(vmDef) && lxcContainerDropCapabilities(!!hasReboot) < 0)
         goto cleanup;
 
     if (lxcContainerSendContinue(argv->handshakefd) < 0) {
@@ -2025,16 +2034,6 @@ cleanup:
     return ret;
 }
 
-static int userns_supported(void)
-{
-    return lxcContainerAvailable(LXC_CONTAINER_FEATURE_USER) == 0;
-}
-
-static int userns_required(virDomainDefPtr def)
-{
-    return def->idmap.uidmap && def->idmap.gidmap;
-}
-
 virArch lxcContainerGetAlt32bitArch(virArch arch)
 {
     /* Any Linux 64bit arch which has a 32bit
-- 
1.8.1.4