Open library file descriptors with O_CLOEXEC
This patch is non-portable, it needs linux 2.6.23 and glibc 2.7
or later, different combinations (old linux, new glibc and vice-versa)
will result in a crash.

To make it portable you have to test O_CLOEXEC support at *runtime*
compile time is not enough.


Index: curl-8.4.0/lib/file.c
===================================================================
--- curl-8.4.0.orig/lib/file.c
+++ curl-8.4.0/lib/file.c
@@ -232,7 +232,7 @@ static CURLcode file_connect(struct Curl
     }
   }
   #else
-  fd = open_readonly(real_path, O_RDONLY);
+  fd = open_readonly(real_path, O_RDONLY|O_CLOEXEC);
   file->path = real_path;
   #endif
 #endif
@@ -318,7 +318,7 @@ static CURLcode file_upload(struct Curl_
   else
     mode = MODE_DEFAULT|O_TRUNC;
 
-  fd = open(file->path, mode, data->set.new_file_perms);
+  fd = open(file->path, mode|O_CLOEXEC, data->set.new_file_perms);
   if(fd < 0) {
     failf(data, "Can't open %s for writing", file->path);
     return CURLE_WRITE_ERROR;
Index: curl-8.4.0/lib/if2ip.c
===================================================================
--- curl-8.4.0.orig/lib/if2ip.c
+++ curl-8.4.0/lib/if2ip.c
@@ -208,7 +208,7 @@ if2ip_result_t Curl_if2ip(int af,
   if(len >= sizeof(req.ifr_name))
     return IF2IP_NOT_FOUND;
 
-  dummy = socket(AF_INET, SOCK_STREAM, 0);
+  dummy = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC, 0);
   if(CURL_SOCKET_BAD == dummy)
     return IF2IP_NOT_FOUND;
 
Index: curl-8.4.0/configure.ac
===================================================================
--- curl-8.4.0.orig/configure.ac
+++ curl-8.4.0/configure.ac
@@ -428,6 +428,8 @@ AC_DEFINE_UNQUOTED(OS, "${host}", [cpu-m
 # Silence warning: ar: 'u' modifier ignored since 'D' is the default
 AC_SUBST(AR_FLAGS, [cr])
 
+AC_USE_SYSTEM_EXTENSIONS
+
 dnl This defines _ALL_SOURCE for AIX
 CURL_CHECK_AIX_ALL_SOURCE
 
Index: curl-8.4.0/lib/hostip.c
===================================================================
--- curl-8.4.0.orig/lib/hostip.c
+++ curl-8.4.0/lib/hostip.c
@@ -44,6 +44,7 @@
 #include <setjmp.h>
 #include <signal.h>
 
+#include <fcntl.h>
 #include "urldata.h"
 #include "sendf.h"
 #include "hostip.h"
@@ -609,7 +610,7 @@ bool Curl_ipv6works(struct Curl_easy *da
   else {
     int ipv6_works = -1;
     /* probe to see if we have a working IPv6 stack */
-    curl_socket_t s = socket(PF_INET6, SOCK_DGRAM, 0);
+    curl_socket_t s = socket(PF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, 0);
     if(s == CURL_SOCKET_BAD)
       /* an IPv6 address was requested but we can't get/use one */
       ipv6_works = 0;
Index: curl-8.4.0/lib/cf-socket.c
===================================================================
--- curl-8.4.0.orig/lib/cf-socket.c
+++ curl-8.4.0/lib/cf-socket.c
@@ -274,7 +274,9 @@ static CURLcode socket_open(struct Curl_
   }
   else {
     /* opensocket callback not set, so simply create the socket now */
-    *sockfd = socket(addr->family, addr->socktype, addr->protocol);
+    *sockfd = socket(addr->family,
+		     addr->socktype|SOCK_CLOEXEC,
+		     addr->protocol);
   }
 
   if(*sockfd == CURL_SOCKET_BAD)