[PATCH v2 07/10] ipcns: Add a limit on the number of ipc namespaces

[Eric W. Biederman]

Signed-off-by: "Eric W. Biederman" <ebied...@xmission.com>
---
 include/linux/user_namespace.h |  1 +
 ipc/namespace.c                | 42 +++++++++++++++++++++++++++++++-----------
 kernel/user_namespace.c        |  1 +
 3 files changed, 33 insertions(+), 11 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index bed2506081fe..367cf08ff63d 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -26,6 +26,7 @@ enum ucounts {
        UCOUNT_USER_NAMESPACES,
        UCOUNT_PID_NAMESPACES,
        UCOUNT_UTS_NAMESPACES,
+       UCOUNT_IPC_NAMESPACES,
        UCOUNT_COUNTS,
 };
 
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 04cb07eb81f1..3996a1e41a1d 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -16,33 +16,42 @@
 
 #include "util.h"
 
+static bool inc_ipc_namespaces(struct user_namespace *ns)
+{
+       return inc_ucount(ns, UCOUNT_IPC_NAMESPACES);
+}
+
+static void dec_ipc_namespaces(struct user_namespace *ns)
+{
+       dec_ucount(ns, UCOUNT_IPC_NAMESPACES);
+}
+
 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
                                           struct ipc_namespace *old_ns)
 {
        struct ipc_namespace *ns;
        int err;
 
+       err = -ENFILE;
+       if (!inc_ipc_namespaces(user_ns))
+               goto fail;
+
+       err = -ENOMEM;
        ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
        if (ns == NULL)
-               return ERR_PTR(-ENOMEM);
+               goto fail_dec;
 
        err = ns_alloc_inum(&ns->ns);
-       if (err) {
-               kfree(ns);
-               return ERR_PTR(err);
-       }
+       if (err)
+               goto fail_free;
        ns->ns.ops = &ipcns_operations;
 
        atomic_set(&ns->count, 1);
        ns->user_ns = get_user_ns(user_ns);
 
        err = mq_init_ns(ns);
-       if (err) {
-               put_user_ns(ns->user_ns);
-               ns_free_inum(&ns->ns);
-               kfree(ns);
-               return ERR_PTR(err);
-       }
+       if (err)
+               goto fail_put;
        atomic_inc(&nr_ipc_ns);
 
        sem_init_ns(ns);
@@ -50,6 +59,16 @@ static struct ipc_namespace *create_ipc_ns(struct 
user_namespace *user_ns,
        shm_init_ns(ns);
 
        return ns;
+
+fail_put:
+       put_user_ns(ns->user_ns);
+       ns_free_inum(&ns->ns);
+fail_free:
+       kfree(ns);
+fail_dec:
+       dec_ipc_namespaces(user_ns);
+fail:
+       return ERR_PTR(err);
 }
 
 struct ipc_namespace *copy_ipcs(unsigned long flags,
@@ -98,6 +117,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
        shm_exit_ns(ns);
        atomic_dec(&nr_ipc_ns);
 
+       dec_ipc_namespaces(ns->user_ns);
        put_user_ns(ns->user_ns);
        ns_free_inum(&ns->ns);
        kfree(ns);
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 6b205c24e888..060d3e099f87 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -79,6 +79,7 @@ static struct ctl_table userns_table[] = {
        UCOUNT_ENTRY("max_user_namespaces"),
        UCOUNT_ENTRY("max_pid_namespaces"),
        UCOUNT_ENTRY("max_uts_namespaces"),
+       UCOUNT_ENTRY("max_ipc_namespaces"),
        { }
 };
 #endif /* CONFIG_SYSCTL */
-- 
2.8.3