diff --git a/mm/nommu.c b/mm/nommu.c
index 28754c4..4bde489 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -919,6 +919,10 @@
 		if (!file->f_op->read)
 			capabilities &= ~BDI_CAP_MAP_COPY;
 
+		/* The file shall have been opened with read permission. */
+		if (!(file->f_mode & FMODE_READ))
+			return -EACCES;
+
 		if (flags & MAP_SHARED) {
 			/* do checks for writing, appending and locking */
 			if ((prot & PROT_WRITE) &&