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authorEric W. Biederman <ebiederm@xmission.com>2017-04-29 21:12:15 +0200
committerEric W. Biederman <ebiederm@xmission.com>2017-07-20 14:43:58 +0200
commita2b426267c56773201f968fdb5eda6ab9ae94e34 (patch)
treeb58af67eb704fcd9d3306b0b725c935a1dbcadae /kernel
parentLinux v4.13-rc1 (diff)
downloadlinux-a2b426267c56773201f968fdb5eda6ab9ae94e34.tar.xz
linux-a2b426267c56773201f968fdb5eda6ab9ae94e34.zip
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 <ktkhai@virtuozzo.com> Ref: 49f4d8b93ccf ("pidns: Capture the user namespace and filter ns_last_pid") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/pid_namespace.c4
-rw-r--r--kernel/user_namespace.c20
2 files changed, 16 insertions, 8 deletions
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;
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 2f735cbe05e8..c490f1e4313b 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -986,17 +986,21 @@ bool userns_may_setgroups(const struct user_namespace *ns)
}
/*
- * Returns true if @ns is the same namespace as or a descendant of
- * @target_ns.
+ * Returns true if @child is the same namespace or a descendant of
+ * @ancestor.
*/
+bool in_userns(const struct user_namespace *ancestor,
+ const struct user_namespace *child)
+{
+ const struct user_namespace *ns;
+ for (ns = child; ns->level > ancestor->level; ns = ns->parent)
+ ;
+ return (ns == ancestor);
+}
+
bool current_in_userns(const struct user_namespace *target_ns)
{
- struct user_namespace *ns;
- for (ns = current_user_ns(); ns; ns = ns->parent) {
- if (ns == target_ns)
- return true;
- }
- return false;
+ return in_userns(target_ns, current_user_ns());
}
static inline struct user_namespace *to_user_ns(struct ns_common *ns)