pidns: Add a limit on the number of pid namespaces

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

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 918b117a7cd303163796af02289afda4eae585ef..34cce96741bc1dfb9966cb8b84da8eb6452464ed 100644 (file)
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -40,6 +40,7 @@ struct pid_namespace {
        struct fs_pin *bacct;
 #endif
        struct user_namespace *user_ns;
+       struct ucounts *ucounts;
        struct work_struct proc_work;
        kgid_t pid_gid;
        int hide_pid;

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 9b676ead35c3a5ad818ca34fb7c45b54002afc11..9ee94827728d90b2cd8af2fb0bc986c24ff01ae4 100644 (file)
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -26,6 +26,7 @@ struct ucounts;
 
 enum ucount_type {
        UCOUNT_USER_NAMESPACES,
+       UCOUNT_PID_NAMESPACES,
        UCOUNT_COUNTS,
 };
 

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index a65ba137fd15b42ba840ca1e46243ef44fa6839c..30a7f335193284d539f6b7cdc17bd488bec36488 100644 (file)
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -79,23 +79,36 @@ static void proc_cleanup_work(struct work_struct *work)
 /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
 #define MAX_PID_NS_LEVEL 32
 
+static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
+{
+       return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
+}
+
+static void dec_pid_namespaces(struct ucounts *ucounts)
+{
+       dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
+}
+
 static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
        struct pid_namespace *parent_pid_ns)
 {
        struct pid_namespace *ns;
        unsigned int level = parent_pid_ns->level + 1;
+       struct ucounts *ucounts;
        int i;
        int err;
 
-       if (level > MAX_PID_NS_LEVEL) {
-               err = -EINVAL;
+       err = -EINVAL;
+       if (level > MAX_PID_NS_LEVEL)
+               goto out;
+       ucounts = inc_pid_namespaces(user_ns);
+       if (!ucounts)
                goto out;
-       }
 
        err = -ENOMEM;
        ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
        if (ns == NULL)
-               goto out;
+               goto out_dec;
 
        ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!ns->pidmap[0].page)
@@ -114,6 +127,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
        ns->level = level;
        ns->parent = get_pid_ns(parent_pid_ns);
        ns->user_ns = get_user_ns(user_ns);
+       ns->ucounts = ucounts;
        ns->nr_hashed = PIDNS_HASH_ADDING;
        INIT_WORK(&ns->proc_work, proc_cleanup_work);
 
@@ -129,6 +143,8 @@ out_free_map:
        kfree(ns->pidmap[0].page);
 out_free:
        kmem_cache_free(pid_ns_cachep, ns);
+out_dec:
+       dec_pid_namespaces(ucounts);
 out:
        return ERR_PTR(err);
 }
@@ -146,6 +162,7 @@ static void destroy_pid_namespace(struct pid_namespace *ns)
        ns_free_inum(&ns->ns);
        for (i = 0; i < PIDMAP_ENTRIES; i++)
                kfree(ns->pidmap[i].page);
+       dec_pid_namespaces(ns->ucounts);
        put_user_ns(ns->user_ns);
        call_rcu(&ns->rcu, delayed_free_pidns);
 }

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 0f9ab3b261854b95c34b5b4c7ecb8dad4e263c4e..66eca94e4ada5f23408a338dc51813671d6b7d19 100644 (file)
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -68,6 +68,7 @@ static int int_max = INT_MAX;
        }
 static struct ctl_table user_table[] = {
        UCOUNT_ENTRY("max_user_namespaces"),
+       UCOUNT_ENTRY("max_pid_namespaces"),
        { }
 };
 #endif /* CONFIG_SYSCTL */