Commit 9d118277 authored by Nick Mathewson's avatar Nick Mathewson 🐛
Browse files

Fix a rare infinite-recursion bug when shutting down.

Once we had called log_free_all(), anything that tried to log a
message (like a failed tor_assert()) would fail like this:

   1. The logging call eventually invokes the _log() function.
   2. _log() calls tor_mutex_lock(log_mutex).
   3. tor_mutex_lock(m) calls tor_assert(m).
   4. Since we freed the log_mutex, tor_assert() fails, and tries to
      log its failure.
   5. GOTO 1.

Now we allocate the mutex statically, and never destroy it on
shutdown.

Bugfix on 0.2.0.16-alpha, which introduced the log mutex.

This bug was found by Matt Edman.
parent c9b8a4a1
......@@ -15,6 +15,9 @@ Changes in version 0.2.1.20 - 2009-??-??
- Fix a signed/unsigned compile warning in 0.2.1.19.
- Fix possible segmentation fault on directory authorities. Bugfix on
0.2.1.14-rc.
- Fix an extremely infinite recursion bug that could occur if we tried
to log a message after shutting down the log subsystem. Found by Matt
Edman. Bugfix on 0.2.0.16-alpha.
Changes in version 0.2.1.19 - 2009-07-28
......
......@@ -94,7 +94,8 @@ should_log_function_name(log_domain_mask_t domain, int severity)
}
/** A mutex to guard changes to logfiles and logging. */
static tor_mutex_t *log_mutex = NULL;
static tor_mutex_t log_mutex;
static int log_mutex_initialized = 0;
/** Linked list of logfile_t. */
static logfile_t *logfiles = NULL;
......@@ -105,9 +106,9 @@ static int syslog_count = 0;
#endif
#define LOCK_LOGS() STMT_BEGIN \
tor_mutex_acquire(log_mutex); \
tor_mutex_acquire(&log_mutex); \
STMT_END
#define UNLOCK_LOGS() STMT_BEGIN tor_mutex_release(log_mutex); STMT_END
#define UNLOCK_LOGS() STMT_BEGIN tor_mutex_release(&log_mutex); STMT_END
/** What's the lowest log level anybody cares about? Checking this lets us
* bail out early from log_debug if we aren't debugging. */
......@@ -448,8 +449,9 @@ logs_free_all(void)
log_free(victim);
}
tor_free(appname);
tor_mutex_free(log_mutex);
log_mutex = NULL;
/* We _could_ destroy the log mutex here, but that would screw up any logs
* that happened between here and the end of execution. */
}
/** Remove and free the log entry <b>victim</b> from the linked-list
......@@ -545,8 +547,10 @@ add_stream_log(const log_severity_list_t *severity,
void
init_logging(void)
{
if (!log_mutex)
log_mutex = tor_mutex_new();
if (!log_mutex_initialized) {
tor_mutex_init(&log_mutex);
log_mutex_initialized = 1;
}
}
/** Add a log handler to receive messages during startup (before the real
......
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