Some systems poll function sets POLLHUP in revents without setting

POLLIN, and sets POLLERR without setting POLLIN and POLLOUT. In some
libcurl code execution paths this could trigger busy wait loops with
high CPU usage until a timeout condition aborted the loop.

This fix for Curl_poll adresses the above in a libcurl-wide mode.

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/select.c b/lib/select.c
index 7d6a6234f..2e1f38e5f 100644
--- a/lib/select.c
+++ b/lib/select.c
@@ -398,6 +398,20 @@ int Curl_poll(struct pollfd ufds[], unsigned int nfds, int timeout_ms)
     }
   } while(r == -1);
 
+  if(r < 0)
+    return -1;
+  if(r == 0)
+    return 0;
+
+  for (i = 0; i < nfds; i++) {
+    if(ufds[i].fd == CURL_SOCKET_BAD)
+      continue;
+    if(ufds[i].revents & POLLHUP)
+      ufds[i].revents |= POLLIN;
+    if(ufds[i].revents & POLLERR)
+      ufds[i].revents |= (POLLIN|POLLOUT);
+  }
+
 #else  /* HAVE_POLL_FINE */
 
   FD_ZERO(&fds_read);