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Call pickup race leaves orphaned channels or crashes.

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Multiple users attempting to pickup a call that has been forked to
multiple extensions either crashes or fails a masquerade with a "bad
things may happen" message.

This is the scenario that is causing all the grief:
1) Pickup target is selected
2) target is marked as being picked up in ast_do_pickup()
3) target is unlocked by ast_do_pickup()
4) app dial or queue gets a chance to hang up losing calls and calls
ast_hangup() on target
5) SINCE A MASQUERADE HAS NOT BEEN SETUP YET BY ast_do_pickup() with
ast_channel_masquerade(), ast_hangup() completes successfully and the
channel is no longer in the channels container.
6) ast_do_pickup() then calls ast_channel_masquerade() to schedule the
masquerade on the dead channel.
7) ast_do_pickup() then calls ast_do_masquerade() on the dead channel
8) bad things happen while doing the masquerade and in the process
ast_do_masquerade() puts the dead channel back into the channels container
9) The "orphaned" channel is visible in the channels list if a crash does
not happen.

This patch does the following:

* Made ast_hangup() set AST_FLAG_ZOMBIE on a successfully hung-up channel
and not release the channel lock until that has happened.

* Made __ast_channel_masquerade() not setup a masquerade if either channel
has AST_FLAG_ZOMBIE set.

* Fix chan_agent misuse of AST_FLAG_ZOMBIE since it would no longer work.

(closes issue ASTERISK-18222)
Reported by: Alec Davis
Tested by: rmudgett, Alec Davis, irroot, Karsten Wemheuer

(closes issue ASTERISK-18273)
Reported by: Karsten Wemheuer
Tested by: rmudgett, Alec Davis, irroot, Karsten Wemheuer

Review: https://reviewboard.asterisk.org/r/1400/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.8@334009 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Richard Mudgett
2011-08-31 15:20:31 +00:00
parent c2636419b4
commit 9e99b1819e
2 changed files with 116 additions and 66 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
channels/chan_agent.c
View File

@@ -1300,10 +1300,8 @@ static int check_availability(struct agent_pvt *newlyavailable, int needlock)
ast_setstate(parent, AST_STATE_UP);
ast_setstate(chan, AST_STATE_UP);
ast_copy_string(parent->context, chan->context, sizeof(parent->context));
/* Go ahead and mark the channel as a zombie so that masquerade will
destroy it for us, and we need not call ast_hangup */
ast_set_flag(chan, AST_FLAG_ZOMBIE);
ast_channel_masquerade(parent, chan);
ast_hangup(chan);
p->abouttograb = 0;
} else {
ast_debug(1, "Sneaky, parent disappeared in the mean time...\n");

132
main/channel.c
View File

@@ -2731,47 +2731,57 @@ void ast_set_hangupsource(struct ast_channel *chan, const char *source, int forc
/*! \brief Hangup a channel */
int ast_hangup(struct ast_channel *chan)
{
int res = 0;
char extra_str[64]; /* used for cel logging below */
/* Don't actually hang up a channel that will masquerade as someone else, or
if someone is going to masquerade as us */
ast_autoservice_stop(chan);
ao2_lock(channels);
ast_channel_lock(chan);
if (chan->audiohooks) {
ast_audiohook_detach_list(chan->audiohooks);
chan->audiohooks = NULL;
}
ast_framehook_list_destroy(chan);
ast_autoservice_stop(chan);
if (chan->masq) {
/*
* Do the masquerade if someone is setup to masquerade into us.
*
* NOTE: We must hold the channel lock after testing for a
* pending masquerade and setting the channel as a zombie to
* prevent __ast_channel_masquerade() from setting up a
* masquerade with a dead channel.
*/
while (chan->masq) {
ast_channel_unlock(chan);
ao2_unlock(channels);
if (ast_do_masquerade(chan)) {
ast_log(LOG_WARNING, "Failed to perform masquerade\n");
/* Abort the loop or we might never leave. */
ao2_lock(channels);
ast_channel_lock(chan);
break;
}
ao2_lock(channels);
ast_channel_lock(chan);
}
if (chan->masq) {
ast_log(LOG_WARNING, "%s getting hung up, but someone is trying to masq into us?!?\n", chan->name);
ast_channel_unlock(chan);
return 0;
}
/* If this channel is one which will be masqueraded into something,
mark it as a zombie already, so we know to free it later */
if (chan->masqr) {
/*
* This channel is one which will be masqueraded into something.
* Mark it as a zombie already so ast_do_masquerade() will know
* to free it later.
*/
ast_set_flag(chan, AST_FLAG_ZOMBIE);
ast_channel_unlock(chan);
ao2_unlock(channels);
return 0;
}
ast_channel_unlock(chan);
ao2_unlink(channels, chan);
ao2_unlock(channels);
ast_channel_lock(chan);
free_translation(chan);
/* Close audio stream */
if (chan->stream) {
@@ -2788,9 +2798,11 @@ int ast_hangup(struct ast_channel *chan)
chan->sched = NULL;
}
if (chan->generatordata) /* Clear any tone stuff remaining */
if (chan->generator && chan->generator->release)
if (chan->generatordata) { /* Clear any tone stuff remaining */
if (chan->generator && chan->generator->release) {
chan->generator->release(chan, chan->generatordata);
}
}
chan->generatordata = NULL;
chan->generator = NULL;
@@ -2805,13 +2817,21 @@ int ast_hangup(struct ast_channel *chan)
}
if (!ast_test_flag(chan, AST_FLAG_ZOMBIE)) {
ast_debug(1, "Hanging up channel '%s'\n", chan->name);
if (chan->tech->hangup)
res = chan->tech->hangup(chan);
/*
* This channel is now dead so mark it as a zombie so anyone
* left holding a reference to this channel will not use it.
*/
ast_set_flag(chan, AST_FLAG_ZOMBIE);
if (chan->tech->hangup) {
chan->tech->hangup(chan);
}
} else {
ast_debug(1, "Hanging up zombie '%s'\n", chan->name);
}
ast_channel_unlock(chan);
ast_cc_offer(chan);
ast_manager_event(chan, EVENT_FLAG_CALL, "Hangup",
"Channel: %s\r\n"
@@ -2836,16 +2856,15 @@ int ast_hangup(struct ast_channel *chan)
!ast_test_flag(chan->cdr, AST_CDR_FLAG_POST_DISABLED) &&
(chan->cdr->disposition != AST_CDR_NULL || ast_test_flag(chan->cdr, AST_CDR_FLAG_DIALED))) {
ast_channel_lock(chan);
ast_cdr_end(chan->cdr);
ast_cdr_detach(chan->cdr);
chan->cdr = NULL;
ast_channel_unlock(chan);
}
chan = ast_channel_release(chan);
ast_channel_unref(chan);
return res;
return 0;
}
int ast_raw_answer(struct ast_channel *chan, int cdr_answer)
@@ -5738,48 +5757,81 @@ static int __ast_channel_masquerade(struct ast_channel *original, struct ast_cha
int res = -1;
struct ast_channel *final_orig, *final_clone, *base;
retrymasq:
for (;;) {
final_orig = original;
final_clone = clonechan;
ast_channel_lock(original);
while (ast_channel_trylock(clonechan)) {
ast_channel_lock_both(original, clonechan);
if (ast_test_flag(original, AST_FLAG_ZOMBIE)
|| ast_test_flag(clonechan, AST_FLAG_ZOMBIE)) {
/* Zombies! Run! */
ast_log(LOG_WARNING,
"Can't setup masquerade. One or both channels is dead. (%s <-- %s)\n",
original->name, clonechan->name);
ast_channel_unlock(clonechan);
ast_channel_unlock(original);
usleep(1);
ast_channel_lock(original);
return -1;
}
/* each of these channels may be sitting behind a channel proxy (i.e. chan_agent)
and if so, we don't really want to masquerade it, but its proxy */
if (original->_bridge && (original->_bridge != ast_bridged_channel(original)) && (original->_bridge->_bridge != original))
/*
* Each of these channels may be sitting behind a channel proxy
* (i.e. chan_agent) and if so, we don't really want to
* masquerade it, but its proxy
*/
if (original->_bridge
&& (original->_bridge != ast_bridged_channel(original))
&& (original->_bridge->_bridge != original)) {
final_orig = original->_bridge;
if (clonechan->_bridge && (clonechan->_bridge != ast_bridged_channel(clonechan)) && (clonechan->_bridge->_bridge != clonechan))
}
if (clonechan->_bridge
&& (clonechan->_bridge != ast_bridged_channel(clonechan))
&& (clonechan->_bridge->_bridge != clonechan)) {
final_clone = clonechan->_bridge;
if (final_clone->tech->get_base_channel && (base = final_clone->tech->get_base_channel(final_clone))) {
}
if (final_clone->tech->get_base_channel
&& (base = final_clone->tech->get_base_channel(final_clone))) {
final_clone = base;
}
if ((final_orig != original) || (final_clone != clonechan)) {
/* Lots and lots of deadlock avoidance. The main one we're competing with
* is ast_write(), which locks channels recursively, when working with a
* proxy channel. */
/*
* Lots and lots of deadlock avoidance. The main one we're
* competing with is ast_write(), which locks channels
* recursively, when working with a proxy channel.
*/
if (ast_channel_trylock(final_orig)) {
ast_channel_unlock(clonechan);
ast_channel_unlock(original);
goto retrymasq;
/* Try again */
continue;
}
if (ast_channel_trylock(final_clone)) {
ast_channel_unlock(final_orig);
ast_channel_unlock(clonechan);
ast_channel_unlock(original);
goto retrymasq;
/* Try again */
continue;
}
ast_channel_unlock(clonechan);
ast_channel_unlock(original);
original = final_orig;
clonechan = final_clone;
if (ast_test_flag(original, AST_FLAG_ZOMBIE)
|| ast_test_flag(clonechan, AST_FLAG_ZOMBIE)) {
/* Zombies! Run! */
ast_log(LOG_WARNING,
"Can't setup masquerade. One or both channels is dead. (%s <-- %s)\n",
original->name, clonechan->name);
ast_channel_unlock(clonechan);
ast_channel_unlock(original);
return -1;
}
}
break;
}
if (original == clonechan) {