Re: [PATCH 02/14] allow root in container to copy namespaces

Quoting Eric W. Biederman (ebiederm@xmission.com):

Serge Hallyn [off-list ref] writes:

quoted

From: Serge E. Hallyn <redacted>

Othewise nested containers with user namespaces won't be possible.

It's true that user namespaces are not yet fully isolated, but for
that same reason there are far worse things that root in a child
user ns can do.  Spawning a child user ns is not in itself bad.

This patch also allows setns for root in a container:
@Eric Biederman: are there gotchas in allowing setns from child
userns?

Yes.  We need to ensure that the target namespaces are namespaces
that have been created in from user_namespace or from a child of this
user_namespace.

Aka we need to ensure that we have CAP_SYS_ADMIN for the new namespace.

Thanks - so the last hunk in this patch is wrong.

Eric

quoted

Signed-off-by: Serge E. Hallyn <redacted>
Cc: Eric W. Biederman <redacted>
---
 kernel/fork.c    |    4 ++--
 kernel/nsproxy.c |    6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 17bf7c8..22d0cf0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c

@@ -1473,8 +1473,8 @@ long do_fork(unsigned long clone_flags,
 		/* hopefully this check will go away when userns support is
 		 * complete
 		 */
-		if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
-				!capable(CAP_SETGID))
+		if (!nsown_capable(CAP_SYS_ADMIN) || !nsown_capable(CAP_SETUID) ||
+				!nsown_capable(CAP_SETGID))
 			return -EPERM;
 	}
 

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 9aeab4b..f50542d 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c

@@ -134,7 +134,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 				CLONE_NEWPID | CLONE_NEWNET)))
 		return 0;
 
-	if (!capable(CAP_SYS_ADMIN)) {
+	if (!nsown_capable(CAP_SYS_ADMIN)) {
 		err = -EPERM;
 		goto out;
 	}

@@ -191,7 +191,7 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
 			       CLONE_NEWNET)))
 		return 0;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!nsown_capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	*new_nsp = create_new_namespaces(unshare_flags, current,

@@ -241,7 +241,7 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype)
 	struct file *file;
 	int err;
 
-	if (!capable(CAP_SYS_ADMIN))
+	if (!nsown_capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
 	file = proc_ns_fget(fd);