chan_dahdi.c: Fix deadlock potential in fax redirection.

The dahdi_handle_dtmf() and my_handle_dtmf() have the potential to
deadlock if an incoming fax happens during the Playback or similar
application.

* Fixed the potential deadlock by not calling ast_async_goto() with the
channel lock held.

ASTERISK-26216 #close
Reported by: Richard Mudgett

Change-Id: I9144b84ade5f96690996624ec8a2d40c56af40aa
changes/48/3248/1
Richard Mudgett 9 years ago
parent fa91cf3eec
commit dcb8aa8c1c

@ -1696,26 +1696,28 @@ static void my_handle_dtmf(void *pvt, struct ast_channel *ast, enum analog_sub a
if (strcmp(ast_channel_exten(ast), "fax")) {
const char *target_context = S_OR(ast_channel_macrocontext(ast), ast_channel_context(ast));
/* We need to unlock 'ast' here because ast_exists_extension has the
/*
* We need to unlock 'ast' here because ast_exists_extension has the
* potential to start autoservice on the channel. Such action is prone
* to deadlock.
* to deadlock if the channel is locked.
*
* ast_async_goto() has its own restriction on not holding the
* channel lock.
*/
ast_mutex_unlock(&p->lock);
ast_channel_unlock(ast);
if (ast_exists_extension(ast, target_context, "fax", 1,
S_COR(ast_channel_caller(ast)->id.number.valid, ast_channel_caller(ast)->id.number.str, NULL))) {
ast_channel_lock(ast);
ast_mutex_lock(&p->lock);
ast_verb(3, "Redirecting %s to fax extension\n", ast_channel_name(ast));
/* Save the DID/DNIS when we transfer the fax call to a "fax" extension */
pbx_builtin_setvar_helper(ast, "FAXEXTEN", ast_channel_exten(ast));
if (ast_async_goto(ast, target_context, "fax", 1))
ast_log(LOG_WARNING, "Failed to async goto '%s' into fax of '%s'\n", ast_channel_name(ast), target_context);
} else {
ast_channel_lock(ast);
ast_mutex_lock(&p->lock);
ast_log(LOG_NOTICE, "Fax detected, but no fax extension\n");
}
ast_channel_lock(ast);
ast_mutex_lock(&p->lock);
} else {
ast_debug(1, "Already in a fax extension, not redirecting\n");
}
@ -7203,26 +7205,28 @@ static void dahdi_handle_dtmf(struct ast_channel *ast, int idx, struct ast_frame
if (strcmp(ast_channel_exten(ast), "fax")) {
const char *target_context = S_OR(ast_channel_macrocontext(ast), ast_channel_context(ast));
/* We need to unlock 'ast' here because ast_exists_extension has the
/*
* We need to unlock 'ast' here because ast_exists_extension has the
* potential to start autoservice on the channel. Such action is prone
* to deadlock.
* to deadlock if the channel is locked.
*
* ast_async_goto() has its own restriction on not holding the
* channel lock.
*/
ast_mutex_unlock(&p->lock);
ast_channel_unlock(ast);
if (ast_exists_extension(ast, target_context, "fax", 1,
S_COR(ast_channel_caller(ast)->id.number.valid, ast_channel_caller(ast)->id.number.str, NULL))) {
ast_channel_lock(ast);
ast_mutex_lock(&p->lock);
ast_verb(3, "Redirecting %s to fax extension\n", ast_channel_name(ast));
/* Save the DID/DNIS when we transfer the fax call to a "fax" extension */
pbx_builtin_setvar_helper(ast, "FAXEXTEN", ast_channel_exten(ast));
if (ast_async_goto(ast, target_context, "fax", 1))
ast_log(LOG_WARNING, "Failed to async goto '%s' into fax of '%s'\n", ast_channel_name(ast), target_context);
} else {
ast_channel_lock(ast);
ast_mutex_lock(&p->lock);
ast_log(LOG_NOTICE, "Fax detected, but no fax extension\n");
}
ast_channel_lock(ast);
ast_mutex_lock(&p->lock);
} else {
ast_debug(1, "Already in a fax extension, not redirecting\n");
}

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