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Prevent a potential race condition and crash when hanging up a channel by removing the channel from the channel list before begining channel tear down.

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This fix may potentially cause problems with CDR backends that access the channel a CDR is associated with via the channel list.  This fix makes the channel unavabile at the time when the CDR backend is invoked.  This has been documented in include/asterisk/cdr.h.

(closes issue #15316)
Reported by: vmarrone
Tested by: mnicholson

Review: https://reviewboard.asterisk.org/r/362/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@219136 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Matthew Nicholson
2009-09-17 14:58:39 +00:00
parent d28e69ad5d
commit ea3f81a68f
3 changed files with 33 additions and 8 deletions
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5
include/asterisk/cdr.h
View File

@@ -112,6 +112,11 @@ int ast_cdr_serialize_variables(struct ast_cdr *cdr, char *buf, size_t size, cha
void ast_cdr_free_vars(struct ast_cdr *cdr, int recur);
int ast_cdr_copy_vars(struct ast_cdr *to_cdr, struct ast_cdr *from_cdr);
/*!\brief CDR backend callback
* \warning CDR backends should NOT attempt to access the channel associated
* with a CDR record. This channel is not guaranteed to exist when the CDR
* backend is invoked.
*/
typedef int (*ast_cdrbe)(struct ast_cdr *cdr);
/*! \brief Allocate a CDR record

2
include/asterisk/channel.h
View File

@@ -515,6 +515,8 @@ enum {
* bridge terminates, this will allow the hangup in the pbx loop to be run instead.
* */
AST_FLAG_BRIDGE_HANGUP_DONT = (1 << 17),
/*! This flag indicates whether the channel is in the channel list or not. */
AST_FLAG_IN_CHANNEL_LIST = (1 << 19),
};
/*! \brief ast_bridge_config flags */

20
main/channel.c
View File

@@ -868,6 +868,8 @@ alertpipe_failed:
tmp->tech = &null_tech;
ast_set_flag(tmp, AST_FLAG_IN_CHANNEL_LIST);
AST_LIST_LOCK(&channels);
AST_LIST_INSERT_HEAD(&channels, tmp, chan_list);
AST_LIST_UNLOCK(&channels);
@@ -1247,17 +1249,22 @@ void ast_channel_free(struct ast_channel *chan)
struct varshead *headp;
struct ast_datastore *datastore = NULL;
char name[AST_CHANNEL_NAME], *dashptr;
int inlist;
headp=&chan->varshead;
inlist = ast_test_flag(chan, AST_FLAG_IN_CHANNEL_LIST);
if (inlist) {
AST_LIST_LOCK(&channels);
if (!AST_LIST_REMOVE(&channels, chan, chan_list)) {
ast_log(LOG_ERROR, "Unable to find channel in list to free. Assuming it has already been done.\n");
if (option_debug)
ast_log(LOG_DEBUG, "Unable to find channel in list to free. Assuming it has already been done.\n");
}
/* Lock and unlock the channel just to be sure nobody has it locked still
due to a reference retrieved from the channel list. */
ast_channel_lock(chan);
ast_channel_unlock(chan);
}
/* Get rid of each of the data stores on the channel */
while ((datastore = AST_LIST_REMOVE_HEAD(&chan->datastores, entry)))
@@ -1328,6 +1335,7 @@ void ast_channel_free(struct ast_channel *chan)
ast_string_field_free_memory(chan);
free(chan);
if (inlist)
AST_LIST_UNLOCK(&channels);
ast_device_state_changed_literal(name);
@@ -1515,6 +1523,16 @@ int ast_hangup(struct ast_channel *chan)
ast_channel_unlock(chan);
return 0;
}
ast_channel_unlock(chan);
AST_LIST_LOCK(&channels);
if (!AST_LIST_REMOVE(&channels, chan, chan_list)) {
ast_log(LOG_ERROR, "Unable to find channel in list to free. Assuming it has already been done.\n");
}
ast_clear_flag(chan, AST_FLAG_IN_CHANNEL_LIST);
AST_LIST_UNLOCK(&channels);
ast_channel_lock(chan);
free_translation(chan);
/* Close audio stream */
if (chan->stream) {