socketpair: clear 'err' when retrying due to EINTR

If the first write was interrupted by a signal and a subsequent write
succeeds, the function would still erroneously return EINTR.

Found by Codex Security
Closes #20809

diff --git a/lib/socketpair.c b/lib/socketpair.c
index 7fd7e30bbab8271c2ff28ebd5d217375371c0d0d..76b959dd4afc698252290be068b482940a041b5e 100644 (file)
--- a/lib/socketpair.c
+++ b/lib/socketpair.c
@@ -317,6 +317,7 @@ int Curl_wakeup_signal(curl_socket_t socks[2])
 #endif
 
   while(1) {
+    err = 0;
     if(wakeup_write(socks[1], buf, sizeof(buf)) < 0) {
       err = SOCKERRNO;
 #ifdef USE_WINSOCK