apparmor: fix: limit the number of levels of policy namespaces

commit 306039414932c80f8420695a24d4fe10c84ccfb2 upstream.

Currently the number of policy namespaces is not bounded relying on
the user namespace limit. However policy namespaces aren't strictly
tied to user namespaces and it is possible to create them and nest
them arbitrarily deep which can be used to exhaust system resource.

Hard cap policy namespaces to the same depth as user namespaces.

Fixes: c88d4c7b049e8 ("AppArmor: core policy routines")
Reported-by: Qualys Security Advisory <qsa@qualys.com>
Reviewed-by: Ryan Lee <ryan.lee@canonical.com>
Reviewed-by: Cengiz Can <cengiz.can@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/apparmor/include/policy_ns.h b/security/apparmor/include/policy_ns.h
index 3df6f804922da3e327bbefd0b9e3af333bc76921..e5704947e86e9685e292872e7a7704b4de775837 100644 (file)
--- a/security/apparmor/include/policy_ns.h
+++ b/security/apparmor/include/policy_ns.h
@@ -18,6 +18,8 @@
 #include "label.h"
 #include "policy.h"
 
+/* Match max depth of user namespaces */
+#define MAX_NS_DEPTH 32
 
 /* struct aa_ns_acct - accounting of profiles in namespace
  * @max_size: maximum space allowed for all profiles in namespace

diff --git a/security/apparmor/policy_ns.c b/security/apparmor/policy_ns.c
index 53d24cf6389360925d417769fb7ceb3e497cf924..5d342ef078e940144554c857cbd8e3f62b5f9de8 100644 (file)
--- a/security/apparmor/policy_ns.c
+++ b/security/apparmor/policy_ns.c
@@ -249,6 +249,8 @@ static struct aa_ns *__aa_create_ns(struct aa_ns *parent, const char *name,
        AA_BUG(!name);
        AA_BUG(!mutex_is_locked(&parent->lock));
 
+       if (parent->level > MAX_NS_DEPTH)
+               return ERR_PTR(-ENOSPC);
        ns = alloc_ns(parent->base.hname, name);
        if (!ns)
                return ERR_PTR(-ENOMEM);