From dcb8aa8c1c1207a6ee0c8f9f158154254ab63ec8 Mon Sep 17 00:00:00 2001 From: Richard Mudgett Date: Tue, 19 Jul 2016 13:18:47 -0500 Subject: 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 --- channels/chan_dahdi.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) (limited to 'channels') diff --git a/channels/chan_dahdi.c b/channels/chan_dahdi.c index e9d0b5bd3..9e0bed701 100644 --- a/channels/chan_dahdi.c +++ b/channels/chan_dahdi.c @@ -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"); } -- cgit v1.2.3