1 files changed, 12 insertions, 3 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;