From a2b426267c56773201f968fdb5eda6ab9ae94e34 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sat, 29 Apr 2017 14:12:15 -0500 Subject: userns,pidns: Verify the userns for new pid namespaces It is pointless and confusing to allow a pid namespace hierarchy and the user namespace hierarchy to get out of sync. The owner of a child pid namespace should be the owner of the parent pid namespace or a descendant of the owner of the parent pid namespace. Otherwise it is possible to construct scenarios where a process has a capability over a parent pid namespace but does not have the capability over a child pid namespace. Which confusingly makes permission checks non-transitive. It requires use of setns into a pid namespace (but not into a user namespace) to create such a scenario. Add the function in_userns to help in making this determination. v2: Optimized in_userns by using level as suggested by: Kirill Tkhai Ref: 49f4d8b93ccf ("pidns: Capture the user namespace and filter ns_last_pid") Signed-off-by: "Eric W. Biederman" --- kernel/pid_namespace.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/pid_namespace.c') diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c index 74a5a7255b4d..4918314893bc 100644 --- a/kernel/pid_namespace.c +++ b/kernel/pid_namespace.c @@ -101,6 +101,10 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns int i; int err; + err = -EINVAL; + if (!in_userns(parent_pid_ns->user_ns, user_ns)) + goto out; + err = -ENOSPC; if (level > MAX_PID_NS_LEVEL) goto out; -- cgit v1.2.3