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plugins: Fix undefined deallocation order in struct plugins

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We use the new function `plugins_free` to define the correct deallocation
order on shutdown, since under normal operation the allocation tree is
organized to allow plugins to terminate and automatically free all dependent
resources. During shutdown the deallocation order is under-defined since
siblings may get freed in any order, but we implicitly rely on them staying
around.
This commit is contained in:
Christian Decker
2020-04-12 15:42:41 +02:00
committed by Rusty Russell
parent 284bd7de0c
commit 27ea47ae37
4 changed files with 37 additions and 1 deletions
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20
lightningd/plugin.h
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@@ -137,6 +137,26 @@ void plugins_add_default_dir(struct plugins *plugins);
*/
void plugins_init(struct plugins *plugins, const char *dev_plugin_debug);
/**
* Free all resources that are held by plugins in the correct order.
*
* This function ensures that the resources dangling off of the plugins struct
* are freed in the correct order. This is necessary since the struct manages
* two orthogonal sets of resources:
*
* - Plugins
* - Hook calls and notifications
*
* The tal hierarchy is organized in a plugin centric way, i.e., the plugins
* may exit in an arbitrary order and they'll unregister pointers in the other
* resources. However this will fail if `tal_free` decides to free one of the
* non-plugin resources (technically a sibling in the allocation tree) before
* the plugins we will get a use-after-free. This function fixes this by
* freeing in the correct order without adding additional child-relationships
* in the allocation structure and without adding destructors.
*/
void plugins_free(struct plugins *plugins);
/**
* Register a plugin for initialization and execution.
*