Treat unexpected returned events from poll as errors

Inspired by libxcb's f0565e8f06aadf760a9065a97b8cf5ab9cbd18de

Resolves https://bugs.freedesktop.org/show_bug.cgi?id=20048

Signed-off-by: Jeremy Huddleston <jeremyhu@apple.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/src/NextEvent.c b/src/NextEvent.c
index b1f7bc7..c8c9dd5 100644
--- a/src/NextEvent.c
+++ b/src/NextEvent.c
@@ -356,7 +356,21 @@ static int IoWait (
     return Select (wf->nfds, &wf->rmask, &wf->wmask, &wf->emask,
 		   wt->wait_time_ptr);
 #else
-    return poll (wf->fdlist, wf->fdlistlen, wt->poll_wait);
+    int ret = poll (wf->fdlist, wf->fdlistlen, wt->poll_wait);
+    /* If poll() returns an event we didn't expect, such as POLLNVAL, treat
+     * it as if it failed. */
+    if(ret >= 0) {
+        nfds_t i;
+        for (i=0; i < wf->fdlistlen; i++) {
+            struct pollfd *fd = &wf->fdlist[i];
+            if (fd->revents & ~fd->events) {
+                ret = -1;
+                errno = EIO;
+                break;
+            }
+        }
+    }
+    return ret;
 #endif
 }