util: use pipe2 if available. Fixes #9311

3 files changed, 9 insertions, 2 deletions

diff --git a/configure.ac b/configure.ac
index b9313875e..605b0a6c4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1058,7 +1058,7 @@ AC_TYPE_UID_T
 # check for library functions
 AC_FUNC_FORK
 AC_FUNC_CHOWN
-AC_CHECK_FUNCS([atoll stat64 strnlen mremap getrlimit setrlimit sysconf initgroups strndup gethostbyname2 getpeerucred getpeereid setresuid getifaddrs freeifaddrs getresgid mallinfo2 malloc_size malloc_usable_size getrusage random srandom stat statfs statvfs wait4 timegm])
+AC_CHECK_FUNCS([atoll stat64 strnlen mremap getrlimit setrlimit sysconf initgroups strndup gethostbyname2 getpeerucred getpeereid setresuid getifaddrs freeifaddrs getresgid mallinfo2 malloc_size malloc_usable_size getrusage random srandom stat statfs statvfs wait4 timegm pipe2])
 
 GN_INTLINCL=""
 GN_LIBINTL="$LTLIBINTL"
diff --git a/meson.build b/meson.build
index 071795337..f92ff946f 100644
--- a/meson.build
+++ b/meson.build
@@ -440,7 +440,7 @@ syscalls = [
   'getpeerucred', 'getpeereid', 'setresuid', 'getifaddrs', 'freeifaddrs',
   'getresgid', 'mallinfo2', 'malloc_size', 'malloc_usable_size', 'getrusage',
   'random', 'srandom', 'stat', 'statfs', 'statvfs', 'wait4', 'timegm',
-  'getaddrinfo', 'initgroups', 'gethostbyname'
+  'getaddrinfo', 'initgroups', 'gethostbyname', 'pipe2'
 ]
 
 str_syscalls = [
diff --git a/src/lib/util/disk.c b/src/lib/util/disk.c
index 5dd06fdfb..3ff67c090 100644
--- a/src/lib/util/disk.c
+++ b/src/lib/util/disk.c
@@ -1250,6 +1250,9 @@ GNUNET_DISK_file_open (const char *fn,
     }
   }
 
+  // Setting O_CLOEXEC after pipe() may introduce
+  // race conditions: https://bugs.gnunet.org/view.php?id=9311
+  // This is no problem if the platform supports pipe2
   fd = open (expfn,
              oflags
 #if O_CLOEXEC
@@ -1417,7 +1420,11 @@ GNUNET_DISK_pipe (enum GNUNET_DISK_PipeFlags pf)
 {
   int fd[2];
 
+#if HAVE_PIPE2 && O_CLOEXEC
+  if (-1 == pipe2 (fd, O_CLOEXEC))
+#else
   if (-1 == pipe (fd))
+#endif
   {
     int eno = errno;