1 files changed, 13 insertions, 0 deletions

diff --git a/lib/libc/stdio/fopen.c b/lib/libc/stdio/fopen.c
index 9cedcda6a4df..a6c0028dbd96 100644
--- a/lib/libc/stdio/fopen.c
+++ b/lib/libc/stdio/fopen.c
@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
 #include "un-namespace.h"
@@ -63,6 +64,18 @@ fopen(file, mode)
 		fp->_flags = 0;			/* release */
 		return (NULL);
 	}
+	/*
+	 * File descriptors are a full int, but _file is only a short.
+	 * If we get a valid file descriptor that is greater than
+	 * SHRT_MAX, then the fd will get sign-extended into an
+	 * invalid file descriptor.  Handle this case by failing the
+	 * open.
+	 */
+	if (f > SHRT_MAX) {
+		_close(f);
+		errno = EMFILE;
+		return (NULL);
+	}
 	fp->_file = f;
 	fp->_flags = flags;
 	fp->_cookie = fp;