--- x/fs/namei.c
+++ y/fs/namei.c
@@ -3533,6 +3533,8 @@ static const char *open_last_lookups(str
 
 	if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
 		got_write = !mnt_want_write(nd->path.mnt);
+		if (!got_write && (open_flag & O_CREAT))
+			return ERR_PTR(-EISDIR);
 		/*
 		 * do _not_ fail yet - we might not need that or fail with
 		 * a different error; let lookup_open() decide; we'll be