log: Close log and err file descriptors before aborting

Part of 31594.

3 files changed, 48 insertions, 6 deletions

diff --git a/src/lib/log/log.c b/src/lib/log/log.c
index 2214d4b59d..4adcc5cf57 100644
--- a/src/lib/log/log.c
+++ b/src/lib/log/log.c
@@ -224,6 +224,7 @@ int log_global_min_severity_ = LOG_NOTICE;
 
 static void delete_log(logfile_t *victim);
 static void close_log(logfile_t *victim);
+static void close_log_sigsafe(logfile_t *victim);
 
 static char *domain_to_string(log_domain_mask_t domain,
                              char *buf, size_t buflen);
@@ -833,6 +834,30 @@ logs_free_all(void)
    * that happened between here and the end of execution. */
 }
 
+/** Close signal-safe log files.
+ * Closing the log files makes the process and OS flush log buffers.
+ *
+ * This function is safe to call from a signal handler. It should only be
+ * called when shutting down the log or err modules. It is currenly called
+ * by the err module, when terminating the process on an abnormal condition.
+ */
+void
+logs_close_sigsafe(void)
+{
+  logfile_t *victim, *next;
+  /* We can't LOCK_LOGS() in a signal handler, because it may call
+   * signal-unsafe functions. And we can't deallocate memory, either. */
+  next = logfiles;
+  logfiles = NULL;
+  while (next) {
+    victim = next;
+    next = next->next;
+    if (victim->needs_close) {
+      close_log_sigsafe(victim);
+    }
+  }
+}
+
 /** Remove and free the log entry <b>victim</b> from the linked-list
  * logfiles (it is probably present, but it might not be due to thread
  * racing issues). After this function is called, the caller shouldn't
@@ -859,13 +884,26 @@ delete_log(logfile_t *victim)
 }
 
 /** Helper: release system resources (but not memory) held by a single
- * logfile_t. */
+ * signal-safe logfile_t. If the log's resources can not be released in
+ * a signal handler, does nothing. */
 static void
-close_log(logfile_t *victim)
+close_log_sigsafe(logfile_t *victim)
 {
   if (victim->needs_close && victim->fd >= 0) {
+    /* We can't do anything useful here if close() fails: we're shutting
+     * down logging, and the err module only does fatal errors. */
     close(victim->fd);
     victim->fd = -1;
+  }
+}
+
+/** Helper: release system resources (but not memory) held by a single
+ * logfile_t. */
+static void
+close_log(logfile_t *victim)
+{
+  if (victim->needs_close) {
+    close_log_sigsafe(victim);
   } else if (victim->is_syslog) {
 #ifdef HAVE_SYSLOG_H
     if (--syslog_count == 0) {
diff --git a/src/lib/log/log.h b/src/lib/log/log.h
index dbc1c47021..360951783e 100644
--- a/src/lib/log/log.h
+++ b/src/lib/log/log.h
@@ -170,6 +170,7 @@ void logs_set_domain_logging(int enabled);
 int get_min_log_level(void);
 void switch_logs_debug(void);
 void logs_free_all(void);
+void logs_close_sigsafe(void);
 void add_temp_log(int min_severity);
 void close_temp_logs(void);
 void rollback_log_changes(void);
diff --git a/src/lib/log/util_bug.c b/src/lib/log/util_bug.c
index c65a91ae9e..3435108848 100644
--- a/src/lib/log/util_bug.c
+++ b/src/lib/log/util_bug.c
@@ -11,6 +11,7 @@
 #include "lib/log/util_bug.h"
 #include "lib/log/log.h"
 #include "lib/err/backtrace.h"
+#include "lib/err/torerr.h"
 #ifdef TOR_UNIT_TESTS
 #include "lib/smartlist_core/smartlist_core.h"
 #include "lib/smartlist_core/smartlist_foreach.h"
@@ -122,16 +123,18 @@ tor_bug_occurred_(const char *fname, unsigned int line,
 }
 
 /**
- * Call the abort() function to kill the current process with a fatal
- * error.
+ * Call the tor_raw_abort_() function to close raw logs, then kill the current
+ * process with a fatal error. But first, close the file-based log file
+ * descriptors, so error messages are written before process termination.
  *
  * (This is a separate function so that we declare it in util_bug.h without
- * including stdlib in all the users of util_bug.h)
+ * including torerr.h in all the users of util_bug.h)
  **/
 void
 tor_abort_(void)
 {
-  abort();
+  logs_close_sigsafe();
+  tor_raw_abort_();
 }
 
 #ifdef _WIN32