Resolve deadlock between SIP registration and channel based functions

In r373424, several reentrancy problems in chan_sip were addressed. As a
result, the SIP channel driver is now properly locking the channel driver
private information in certain operations that it wasn't previously. This
exposed two latent problems either in register_verify or by functions called
by register_verify. This includes:
 * Holding the private lock while calling sip_send_mwi_to_peer. This can create
   a new sip_pvt via sip_alloc, which will obtain the channel container lock.
   This is a locking inversion, as any channel related lock must be obtained
   prior to obtaining the SIP channel technology private lock.

   Note that this issue was already fixed in Asterisk 11.

 * Holding the private lock while calling sip_poke_peer. In the same vein as
   sip_send_mwi_to_peer, sip_poke_peer can create a new SIP private, causing
   the same locking inversion.

Note that this locking inversion typically occured when CLI commands were run
while a SIP REGISTER request was being processed, as many CLI commands (such
as 'sip show channels', 'core show channels', etc.) have to obtain the channel
container lock.

(issue ASTERISK-21068)
Reported by: Nicolas Bouliane

(issue ASTERISK-20550)
Reported by: David Brillert

(issue ASTERISK-21314)
Reported by: Badalian Vyacheslav

(issue ASTERISK-21296)
Reported by: Gabriel Birke
........

Merged revisions 383863 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 383878 from http://svn.asterisk.org/svn/asterisk/branches/11

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@383879 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 28e8d4d354df027a8cedaa070bc472aabc5b3646..82a8519d03c4a494185c725097d52f1184debfc4 100644 (file)
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -16131,7 +16131,9 @@ static enum parse_register_result parse_register_contact(struct sip_pvt *pvt, st
                ast_verb(3, "Registered SIP '%s' at %s\n", peer->name,
                        ast_sockaddr_stringify(&peer->addr));
        }
+       sip_pvt_unlock(pvt);
        sip_poke_peer(peer, 0);
+       sip_pvt_lock(pvt);
        register_peer_exten(peer, 1);
 
        /* Save User agent */
@@ -17163,9 +17165,9 @@ static enum check_auth_result register_verify(struct sip_pvt *p, struct ast_sock
        }
        if (!res) {
                if (send_mwi) {
-                       ao2_unlock(p);
+                       sip_pvt_unlock(p);
                        sip_send_mwi_to_peer(peer, 0);
-                       ao2_lock(p);
+                       sip_pvt_lock(p);
                } else {
                        update_peer_lastmsgssent(peer, -1, 0);
                }
@@ -29611,6 +29613,9 @@ static int sip_poke_noanswer(const void *data)
 \note  This is done with 60 seconds between each ping,
        unless forced by cli or manager. If peer is unreachable,
        we check every 10th second by default.
+\note Do *not* hold a pvt lock while calling this function.
+       This function calls sip_alloc, which can cause a deadlock
+       if another sip_pvt is held.
 */
 static int sip_poke_peer(struct sip_peer *peer, int force)
 {