chan_sip: Prevent deadlock when performing BYE with Also transfer.
When a BYE with an Also header is successfully processed, and the sender of the BYE is bridged with another channel, chan_sip will unlock the owner of the dialog on which the BYE was received, call ast_async_goto() on the bridged channel, and then re-lock the owner. The reason for this locking behavior is that ast_async_goto() can result in a masquerade, which requires that the involved channels are unlocked. The problem here is that this causes a locking inversion since the dialog's lock is held when re-locking the owner channel after the async goto. The lock order is supposed to be channel and then sip_pvt. The fix proposed is simple. In addition to unlocking the owner channel before the ast_async_goto() call, also unlock the sip_pvt. Then relock both after ast_async_goto() returns, being sure to lock the channel and then the sip_pvt. ASTERISK-25139 #close Reported by Gregory Massel Change-Id: I72c4fc295ec8573bee599e8e9213c5350a3cd224
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@ -26977,11 +26977,14 @@ static int handle_request_bye(struct sip_pvt *p, struct sip_request *req)
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if (bridged_to) {
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/* Don't actually hangup here... */
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ast_queue_control(c, AST_CONTROL_UNHOLD);
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sip_pvt_unlock(p);
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ast_channel_unlock(c); /* async_goto can do a masquerade, no locks can be held during a masq */
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ast_async_goto(bridged_to, p->context, p->refer->refer_to, 1);
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ast_channel_lock(c);
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} else
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sip_pvt_lock(p);
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} else {
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ast_queue_hangup(p->owner);
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}
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}
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} else {
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ast_log(LOG_WARNING, "Invalid transfer information from '%s'\n", ast_sockaddr_stringify(&p->recv));
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