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Do not send Libevent log messages to a controller (0.2.1 backport)

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Doing so could make Libevent call Libevent from inside a Libevent
logging call, which is a recipe for reentrant confusion and
hard-to-debug crashes.  This would especially hurt if Libevent
debug-level logging is enabled AND the user has a controller
watching for low-severity log messages.

Fix bug 2190; fix on 0.1.0.2-rc.
This commit is contained in:
Nick Mathewson 2010-11-19 22:22:43 -05:00
parent 566a115be1
commit 668f7a2639
3 changed files with 19 additions and 5 deletions
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6
changes/bug2190 Normal file
View File

@ -0,0 +1,6 @@
o Minor bugfixes
- Prevent calls from Libevent from inside Libevent log handlers.
This had potential to cause a nasty set of crashes, especially if
running Libevent with debug logging enabled, and running Tor
with a controller watching for low-severity log messages.
Bugfix on 0.1.0.2-rc. Fixes bug 2190.

14
src/common/log.c
View File

@ -280,6 +280,10 @@ logv(int severity, log_domain_mask_t domain, const char *funcname,
lf = lf->next;
continue;
}
if (lf->callback && (domain & LD_NOCB)) {
lf = lf->next;
continue;
}
if (lf->seems_dead) {
lf = lf->next;
continue;
@ -943,19 +947,19 @@ libevent_logging_callback(int severity, const char *msg)
}
switch (severity) {
case _EVENT_LOG_DEBUG:
log(LOG_DEBUG, LD_NET, "Message from libevent: %s", buf);
log(LOG_DEBUG, LD_NOCB|LD_NET, "Message from libevent: %s", buf);
break;
case _EVENT_LOG_MSG:
log(LOG_INFO, LD_NET, "Message from libevent: %s", buf);
log(LOG_INFO, LD_NOCB|LD_NET, "Message from libevent: %s", buf);
break;
case _EVENT_LOG_WARN:
log(LOG_WARN, LD_GENERAL, "Warning from libevent: %s", buf);
log(LOG_WARN, LD_NOCB|LD_GENERAL, "Warning from libevent: %s", buf);
break;
case _EVENT_LOG_ERR:
log(LOG_ERR, LD_GENERAL, "Error from libevent: %s", buf);
log(LOG_ERR, LD_NOCB|LD_GENERAL, "Error from libevent: %s", buf);
break;
default:
log(LOG_WARN, LD_GENERAL, "Message [%d] from libevent: %s",
log(LOG_WARN, LD_NOCB|LD_GENERAL, "Message [%d] from libevent: %s",
severity, buf);
break;
}

4
src/common/log.h
View File

@ -94,6 +94,10 @@
/** Number of logging domains in the code. */
#define N_LOGGING_DOMAINS 19
/** This log message is not safe to send to a callback-based logger.
* Used as a flag, not a log domain. */
#define LD_NOCB (1u<<31)
typedef uint32_t log_domain_mask_t;
/** Configures which severities are logged for each logging domain for a given