Description: Don't add descriptor over FD_SETSIZE to fd_set
 ConnectionNumber in X11_Pending may return a value outside of the range [0,
 FD_SETSIZE). This value cannot be stored inside a fd_set and will crash the
 program.
 .
 This buffer overflow problem occasionally happens when a lot of file
 descriptors are used.
Author: Sven Eckelmann <sven@narfation.org>

---
diff --git a/src/video/x11/SDL_x11events.c b/src/video/x11/SDL_x11events.c
index 818ab2e21d96fa80c0b6ba72551198e5e9f925b2..5a983208a1a7c5d7d3a1a88bfac0c4337a2f4ed1 100644
--- a/src/video/x11/SDL_x11events.c
+++ b/src/video/x11/SDL_x11events.c
@@ -917,6 +917,9 @@ X11_Pending(Display * display)
         fd_set fdset;
 
         x11_fd = ConnectionNumber(display);
+        if (x11_fd >= FD_SETSIZE || x11_fd < 0)
+            return 0;
+
         FD_ZERO(&fdset);
         FD_SET(x11_fd, &fdset);
         if (select(x11_fd + 1, &fdset, NULL, NULL, &zero_time) == 1) {