3 files changed, 21 insertions, 10 deletions

diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index e5c4f609f22c..e4e47f647446 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -330,8 +330,16 @@ static struct dentry *mqueue_mount(struct file_system_type *fs_type,
                          int flags, const char *dev_name,
                          void *data)
 {
-        if (!(flags & MS_KERNMOUNT))
-                data = current->nsproxy->ipc_ns;
+        if (!(flags & MS_KERNMOUNT)) {
+                struct ipc_namespace *ns = current->nsproxy->ipc_ns;
+                /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
+                 * over the ipc namespace.
+                 */
+                if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+                        return ERR_PTR(-EPERM);
+
+                data = ns;
+        }
         return mount_ns(fs_type, flags, data, mqueue_fill_super);
 }
 
@@ -840,7 +848,8 @@ out_putfd:
                 fd = error;
         }
         mutex_unlock(&root->d_inode->i_mutex);
-        mnt_drop_write(mnt);
+        if (!ro)
+                mnt_drop_write(mnt);
 out_putname:
         putname(name);
         return fd;
diff --git a/ipc/msg.c b/ipc/msg.c
index 31cd1bf6af27..fede1d06ef30 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -872,6 +872,7 @@ long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
                                                         goto out_unlock;
                                                 break;
                                         }
+                                        msg = ERR_PTR(-EAGAIN);
                                 } else
                                         break;
                                 msg_counter++;
diff --git a/ipc/util.c b/ipc/util.c
index 464a8abd779f..03eadd8fb0fd 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -23,6 +23,7 @@
 #include <linux/msg.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
+#include <linux/notifier.h>
 #include <linux/capability.h>
 #include <linux/highuid.h>
 #include <linux/security.h>
@@ -47,19 +48,16 @@ struct ipc_proc_iface {
         int (*show)(struct seq_file *, void *);
 };
 
-#ifdef CONFIG_MEMORY_HOTPLUG
-
 static void ipc_memory_notifier(struct work_struct *work)
 {
         ipcns_notify(IPCNS_MEMCHANGED);
 }
 
-static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
-
-
 static int ipc_memory_callback(struct notifier_block *self,
                                 unsigned long action, void *arg)
 {
+        static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
+
         switch (action) {
         case MEM_ONLINE:    /* memory successfully brought online */
         case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
@@ -85,7 +83,10 @@ static int ipc_memory_callback(struct notifier_block *self,
         return NOTIFY_OK;
 }
 
-#endif /* CONFIG_MEMORY_HOTPLUG */
+static struct notifier_block ipc_memory_nb = {
+        .notifier_call = ipc_memory_callback,
+        .priority = IPC_CALLBACK_PRI,
+};
 
 /**
  *      ipc_init        -       initialise IPC subsystem
@@ -102,7 +103,7 @@ static int __init ipc_init(void)
         sem_init();
         msg_init();
         shm_init();
-        hotplug_memory_notifier(ipc_memory_callback, IPC_CALLBACK_PRI);
+        register_hotmemory_notifier(&ipc_memory_nb);
         register_ipcns_notifier(&init_ipc_ns);
         return 0;
 }