ipcns: Add a limit on the number of ipc namespaces

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

4 files changed, 37 insertions, 11 deletions

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index d10e54f03c09..848e5796400e 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -58,6 +58,7 @@ struct ipc_namespace {
 
         /* user_ns which owns the ipc ns */
         struct user_namespace *user_ns;
+        struct ucounts *ucounts;
 
         struct ns_common ns;
 };
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index f9df7dd2609a..e1d672186f00 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -28,6 +28,7 @@ enum ucount_type {
         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 d87e6baa1323..730914214135 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -16,39 +16,61 @@
 
 #include "util.h"
 
+static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
+{
+        return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
+}
+
+static void dec_ipc_namespaces(struct ucounts *ucounts)
+{
+        dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
+}
+
 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
                                            struct ipc_namespace *old_ns)
 {
         struct ipc_namespace *ns;
+        struct ucounts *ucounts;
         int err;
 
+        err = -ENFILE;
+        ucounts = inc_ipc_namespaces(user_ns);
+        if (!ucounts)
+                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);
+        ns->ucounts = ucounts;
 
         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;
 
         sem_init_ns(ns);
         msg_init_ns(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(ucounts);
+fail:
+        return ERR_PTR(err);
 }
 
 struct ipc_namespace *copy_ipcs(unsigned long flags,
@@ -96,6 +118,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
         msg_exit_ns(ns);
         shm_exit_ns(ns);
 
+        dec_ipc_namespaces(ns->ucounts);
         put_user_ns(ns->user_ns);
         ns_free_inum(&ns->ns);
         kfree(ns);
diff --git a/kernel/ucount.c b/kernel/ucount.c
index 866850e2eb92..fbab75424da6 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -70,6 +70,7 @@ static struct ctl_table user_table[] = {
         UCOUNT_ENTRY("max_user_namespaces"),
         UCOUNT_ENTRY("max_pid_namespaces"),
         UCOUNT_ENTRY("max_uts_namespaces"),
+        UCOUNT_ENTRY("max_ipc_namespaces"),
         { }
 };
 #endif /* CONFIG_SYSCTL */