Split lines before logging in log_from_pipe().

This patch ensures that we work on lines using
tor_get_lines_from_handle() instead of a raw buffer possibly containing
multiple lines from get_string_from_pipe().

See: #21765

src/common/util.c

@@ -5287,11 +5287,11 @@ static int
 log_from_pipe(int fd, int severity, const char *executable,
               int *child_status)
 {
-  char buf[256];
+  smartlist_t *lines = NULL;
   enum stream_status r;
 
   for (;;) {
-    r = get_string_from_pipe(fd, buf, sizeof(buf) - 1);
+    lines = tor_get_lines_from_handle(fd, &r);
 
     if (r == IO_STREAM_CLOSED) {
       return 1;
@@ -5302,13 +5302,20 @@ log_from_pipe(int fd, int severity, const char *executable,
     }
 
     tor_assert(r == IO_STREAM_OKAY);
+    tor_assert(lines != NULL);
 
-    /* Check if buf starts with SPAWN_ERROR_MESSAGE */
-    if (strcmpstart(buf, SPAWN_ERROR_MESSAGE) == 0) {
-      log_portfw_spawn_error_message(buf, executable, child_status);
-    } else {
-      log_fn(severity, LD_GENERAL, "Port forwarding helper says: %s", buf);
-    }
+    SMARTLIST_FOREACH_BEGIN(lines, char *, line) {
+      /* Check if line starts with SPAWN_ERROR_MESSAGE */
+      if (strcmpstart(line, SPAWN_ERROR_MESSAGE) == 0) {
+        log_portfw_spawn_error_message(line, executable, child_status);
+      } else {
+        log_fn(severity, LD_GENERAL, "Port forwarding helper says: %s", line);
+      }
+
+      tor_free(line);
+    } SMARTLIST_FOREACH_END(line);
+
+    smartlist_free(lines);
   }
 
   /* We should never get here */