From f274fc5c685ac245d1d2818046bbfb4b97685211 Mon Sep 17 00:00:00 2001
From: Stefan Eissing <stefan@eissing.org>
Date: Thu, 22 Feb 2024 09:01:06 +0100
Subject: [PATCH] multi: fix multi_sock handling of select_bits

- OR the event bitmask to data->state.select_bits instead of overwriting
  them. They are cleared again on use.

Reported-by: 5533asdg on github
Fixes #12971
Closes #12972
---
 lib/multi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/multi.c b/lib/multi.c
index 48a92928c8..6efd164ee2 100644
--- a/lib/multi.c
+++ b/lib/multi.c
@@ -3243,7 +3243,7 @@ static CURLMcode multi_socket(struct Curl_multi *multi,
 
         if(data->conn && !(data->conn->handler->flags & PROTOPT_DIRLOCK))
           /* set socket event bitmask if they're not locked */
-          data->state.select_bits = (unsigned char)ev_bitmask;
+          data->state.select_bits |= (unsigned char)ev_bitmask;
 
         Curl_expire(data, 0, EXPIRE_RUN_NOW);
       }