<p>Paulo Vicentini has uploaded this change for <strong>review</strong>.</p><p><a href="https://gerrit.asterisk.org/10601">View Change</a></p><pre style="font-family: monospace,monospace; white-space: pre-wrap;">res/res_pjsip: Fix crash due to misuse of session->media between threads.<br><br>This patch makes sure that thread running ast_taskprocessor_execute<br>cannot suddenly dispose the session->media object making the other<br>threads (running pbx_thread / bridge_channel_ind_thread) crash when they<br>try to access the pointer to invalid memory. We were experiencing a crash due<br>to a misuse of session->media container between threads running<br>(bridge_channel_ind_thread/pbx_thread) and the thread running<br>ast_taskprocessor_execute. Depending on the SIP flow (during a disconnection)<br>and the threads' code path, the session->media container was being destroyed<br>(and set to NULL) by the thread running ast_taskprocessor_execute while the<br>thread running t38_framehook_read was still referring to it.<br>Now the "parent" thread bumps the session->media's refcount on behalf of the new<br>thread before the object is passed.The new thread decrements refcount before<br>terminating.<br><br>ASTERISK-28156<br><br>Change-Id: Ia92e2389b8d804bf205473e92ec06217e87ce237<br>---<br>M include/asterisk/res_pjsip_session.h<br>M res/res_pjsip_session.c<br>M res/res_pjsip_t38.c<br>3 files changed, 25 insertions(+), 4 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;">git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/01/10601/1</pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/include/asterisk/res_pjsip_session.h b/include/asterisk/res_pjsip_session.h</span><br><span>index 0c2b1e3..79fda6c 100644</span><br><span>--- a/include/asterisk/res_pjsip_session.h</span><br><span>+++ b/include/asterisk/res_pjsip_session.h</span><br><span>@@ -159,6 +159,8 @@</span><br><span> unsigned int defer_end:1;</span><br><span> /*! Session end (remote hangup) requested while termination deferred */</span><br><span> unsigned int ended_while_deferred:1;</span><br><span style="color: hsl(120, 100%, 40%);">+ /*! Session has ended (i.e. session_end has been called) */</span><br><span style="color: hsl(120, 100%, 40%);">+ unsigned int ended:1;</span><br><span> /*! DTMF mode to use with this session, from endpoint but can change */</span><br><span> enum ast_sip_dtmf_mode dtmf;</span><br><span> /*! Initial incoming INVITE Request-URI. NULL otherwise. */</span><br><span>diff --git a/res/res_pjsip_session.c b/res/res_pjsip_session.c</span><br><span>index 669315f..eedc0f1 100644</span><br><span>--- a/res/res_pjsip_session.c</span><br><span>+++ b/res/res_pjsip_session.c</span><br><span>@@ -1319,7 +1319,9 @@</span><br><span> </span><br><span> ast_taskprocessor_unreference(session->serializer);</span><br><span> ao2_cleanup(session->datastores);</span><br><span style="color: hsl(0, 100%, 40%);">- ao2_cleanup(session->media);</span><br><span style="color: hsl(120, 100%, 40%);">+ if (!session->ended) {</span><br><span style="color: hsl(120, 100%, 40%);">+ ao2_cleanup(session->media);</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span> </span><br><span> AST_LIST_HEAD_DESTROY(&session->supplements);</span><br><span> while ((delay = AST_LIST_REMOVE_HEAD(&session->delayed_requests, next))) {</span><br><span>@@ -2564,7 +2566,11 @@</span><br><span> </span><br><span> /* Release any media resources. */</span><br><span> ao2_cleanup(session->media);</span><br><span style="color: hsl(0, 100%, 40%);">- session->media = NULL;</span><br><span style="color: hsl(120, 100%, 40%);">+ /*</span><br><span style="color: hsl(120, 100%, 40%);">+ * We are sharing ownership with other threads also</span><br><span style="color: hsl(120, 100%, 40%);">+ * using session->media directly</span><br><span style="color: hsl(120, 100%, 40%);">+ */</span><br><span style="color: hsl(120, 100%, 40%);">+ session->ended = 1;</span><br><span> </span><br><span> return 0;</span><br><span> }</span><br><span>diff --git a/res/res_pjsip_t38.c b/res/res_pjsip_t38.c</span><br><span>index cff625f..3eccc6e 100644</span><br><span>--- a/res/res_pjsip_t38.c</span><br><span>+++ b/res/res_pjsip_t38.c</span><br><span>@@ -485,10 +485,20 @@</span><br><span> {</span><br><span> struct ast_sip_channel_pvt *channel = ast_channel_tech_pvt(chan);</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- if (event == AST_FRAMEHOOK_EVENT_READ) {</span><br><span style="color: hsl(120, 100%, 40%);">+ switch (event) {</span><br><span style="color: hsl(120, 100%, 40%);">+ case AST_FRAMEHOOK_EVENT_READ:</span><br><span> f = t38_framehook_read(chan, channel->session, f);</span><br><span style="color: hsl(0, 100%, 40%);">- } else if (event == AST_FRAMEHOOK_EVENT_WRITE) {</span><br><span style="color: hsl(120, 100%, 40%);">+ break;</span><br><span style="color: hsl(120, 100%, 40%);">+ case AST_FRAMEHOOK_EVENT_WRITE:</span><br><span> f = t38_framehook_write(chan, channel->session, f);</span><br><span style="color: hsl(120, 100%, 40%);">+ break;</span><br><span style="color: hsl(120, 100%, 40%);">+ case AST_FRAMEHOOK_EVENT_DETACHED:</span><br><span style="color: hsl(120, 100%, 40%);">+ if (channel->session && channel->session->media) {</span><br><span style="color: hsl(120, 100%, 40%);">+ ao2_ref(channel->session->media, -1);</span><br><span style="color: hsl(120, 100%, 40%);">+ }</span><br><span style="color: hsl(120, 100%, 40%);">+ break;</span><br><span style="color: hsl(120, 100%, 40%);">+ case AST_FRAMEHOOK_EVENT_ATTACHED:</span><br><span style="color: hsl(120, 100%, 40%);">+ break;</span><br><span> }</span><br><span> </span><br><span> return f;</span><br><span>@@ -562,6 +572,9 @@</span><br><span> }</span><br><span> </span><br><span> ast_channel_datastore_add(session->channel, datastore);</span><br><span style="color: hsl(120, 100%, 40%);">+</span><br><span style="color: hsl(120, 100%, 40%);">+ /* bump media container to be used by pbx and bridge threads */</span><br><span style="color: hsl(120, 100%, 40%);">+ ao2_bump(session->media);</span><br><span> ast_channel_unlock(session->channel);</span><br><span> }</span><br><span> </span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.asterisk.org/10601">change 10601</a>. 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<div style="display:none"> Gerrit-Project: asterisk </div>
<div style="display:none"> Gerrit-Branch: 13 </div>
<div style="display:none"> Gerrit-MessageType: newchange </div>
<div style="display:none"> Gerrit-Change-Id: Ia92e2389b8d804bf205473e92ec06217e87ce237 </div>
<div style="display:none"> Gerrit-Change-Number: 10601 </div>
<div style="display:none"> Gerrit-PatchSet: 1 </div>
<div style="display:none"> Gerrit-Owner: Paulo Vicentini <paulo.vicentini@gmail.com> </div>