1 files changed, 31 insertions, 0 deletions

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index e9c9adc84ca6..a8968396046d 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -191,9 +191,40 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
         return;
 }
 
+static int pid_ns_ctl_handler(struct ctl_table *table, int write,
+                void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        struct ctl_table tmp = *table;
+
+        if (write && !capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        /*
+         * Writing directly to ns' last_pid field is OK, since this field
+         * is volatile in a living namespace anyway and a code writing to
+         * it should synchronize its usage with external means.
+         */
+
+        tmp.data = &current->nsproxy->pid_ns->last_pid;
+        return proc_dointvec(&tmp, write, buffer, lenp, ppos);
+}
+
+static struct ctl_table pid_ns_ctl_table[] = {
+        {
+                .procname = "ns_last_pid",
+                .maxlen = sizeof(int),
+                .mode = 0666, /* permissions are checked in the handler */
+                .proc_handler = pid_ns_ctl_handler,
+        },
+        { }
+};
+
+static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
+
 static __init int pid_namespaces_init(void)
 {
         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
+        register_sysctl_paths(kern_path, pid_ns_ctl_table);
         return 0;
 }