core_unreal: Fix deadlock with T.38 control frames.

When using the ast_unreal_lock_all function no channel
locks can be held before calling it.

This change unlocks the channel that indicate was
called on before doing so and then relocks it afterwards.

ASTERISK-29035

Change-Id: Id65016201b5f9c9519a216e250f9101c629e19e9

diff --git a/main/core_unreal.c b/main/core_unreal.c
index 5adc90d2f7e476133f85a9b298b588d65ee4efa0..a79fca417fd53e6b7e2211e1fd07625f8ca4c2e9 100644 (file)
--- a/main/core_unreal.c
+++ b/main/core_unreal.c
@@ -710,6 +710,7 @@ int ast_unreal_indicate(struct ast_channel *ast, int condition, const void *data
                         * signaling and we need to be sure that the locking order is the same to prevent possible
                         * deadlocks.
                         */
+                       ast_channel_unlock(ast);
                        ast_unreal_lock_all(p, &chan, &owner);
 
                        if (owner) {
@@ -726,12 +727,14 @@ int ast_unreal_indicate(struct ast_channel *ast, int condition, const void *data
                        }
 
                        ao2_unlock(p);
+                       ast_channel_lock(ast);
                } else if (parameters->request_response == AST_T38_TERMINATED) {
                        /*
                         * Lock both parts of the local channel so we can restore their topologies to the original.
                         * The topology should be on the unreal_pvt structure, with a ref that we can steal. Same
                         * conditions as above.
                         */
+                       ast_channel_unlock(ast);
                        ast_unreal_lock_all(p, &chan, &owner);
 
                        if (owner) {
@@ -745,6 +748,7 @@ int ast_unreal_indicate(struct ast_channel *ast, int condition, const void *data
                        }
 
                        ao2_unlock(p);
+                       ast_channel_lock(ast);
                }
 
                /*