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# Application framework

## Foreword

This document describes application framework fundamentals.  
FCS (Fully Conform to Specification) implementation is still under development.  
It may happen that current implementation somehow diverges with specifications.

## Overview

The application framework on top of the security framework
provides components to install and uninstall applications
as well as to run them in a secured environment.

The goal of the framework is to manage applications and hide security details
to applications.

For the reasons explained in introduction, it was choose not to reuse Tizen
application framework directly, but to rework a new framework inspired from Tizen.

fundamentals remain identical: the applications are distributed
in a digitally signed container that should match widget specifications
normalized by the W3C.  
This is described by the technical recommendations 
[Packaged Web Apps (Widgets)](http://www.w3.org/TR/widgets) and 
[XML Digital Signatures for Widgets](http://www.w3.org/TR/widgets-digsig)
 of the W3 consortium.

As today this model allows the distribution of HTML, QML and binary applications
but it could be extended to any other class of applications.

The management of widget package signatures.  
Current model is only an initial step, it might be extended in the
future to include new feature (ie: incremental delivery).
: #dd2200; background-color: #fff0f0 } /* Literal.String.Delimiter */ .highlight .sd { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Doc */ .highlight .s2 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Double */ .highlight .se { color: #0044dd; background-color: #fff0f0 } /* Literal.String.Escape */ .highlight .sh { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Heredoc */ .highlight .si { color: #3333bb; background-color: #fff0f0 } /* Literal.String.Interpol */ .highlight .sx { color: #22bb22; background-color: #f0fff0 } /* Literal.String.Other */ .highlight .sr { color: #008800; background-color: #fff0ff } /* Literal.String.Regex */ .highlight .s1 { color: #dd2200; background-color: #fff0f0 } /* Literal.String.Single */ .highlight .ss { color: #aa6600; background-color: #fff0f0 } /* Literal.String.Symbol */ .highlight .bp { color: #003388 } /* Name.Builtin.Pseudo */ .highlight .fm { color: #0066bb; font-weight: bold } /* Name.Function.Magic */ .highlight .vc { color: #336699 } /* Name.Variable.Class */ .highlight .vg { color: #dd7700 } /* Name.Variable.Global */ .highlight .vi { color: #3333bb } /* Name.Variable.Instance */ .highlight .vm { color: #336699 } /* Name.Variable.Magic */ .highlight .il { color: #0000DD; font-weight: bold } /* Literal.Number.Integer.Long */
From 16f63a3c8fa227625bade5a9edea22354b347d18 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Barnab=C3=A1s=20P=C5=91cze?= <pobrn@protonmail.com>
Date: Fri, 18 Feb 2022 18:36:36 +0100
Subject: [PATCH] Revert "loop: remove destroy list"

This reverts commit c474846c42967c44db069a23b76a29da6f496f33.
In addition, `s->loop` is also checked before dispatching a source.

The destroy list is needed in the presence of threads. The
issue is that a source may be destroyed between `epoll_wait()`
returning and thread loop lock being acquired. If this
source is active, then a use-after-free will be triggered
when the thread loop acquires the lock and starts dispatching
the sources.

  thread 1                       thread 2
 ----------                     ----------
                                loop_iterate
                                  spa_loop_control_hook_before
                                    // release lock

 pw_thread_loop_lock

                                  spa_system_pollfd_wait
                                    // assume it returns with source A

 pw_loop_destroy_source(..., A)
  // frees storage of A

 pw_thread_loop_unlock
                                  spa_loop_control_hook_after
                                    // acquire the lock

                                  for (...) {
                                    struct spa_source *s = ep[i].data;
                                    s->rmask = ep[i].events;
                                      // use-after-free if `s` refers to
                                      // the previously freed `A`

Fixes #2147

Upstream-Status: Backport [https://gitlab.freedesktop.org/pipewire/pipewire/-/commit/16f63a3c]
Signed-off-by: Scott Murray <scott.murray@konsulko.com>

---
 spa/plugins/support/loop.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/spa/plugins/support/loop.c b/spa/plugins/support/loop.c
index 0588ce770..04739eb2a 100644
--- a/spa/plugins/support/loop.c
+++ b/spa/plugins/support/loop.c
@@ -75,6 +75,7 @@ struct impl {
         struct spa_system *system;
 
 	struct spa_list source_list;
+	struct spa_list destroy_list;
 	struct spa_hook_list hooks_list;
 
 	int poll_fd;
@@ -325,6 +326,14 @@ static void loop_leave(void *object)
 		impl->thread = 0;
 }
 
+static inline void process_destroy(struct impl *impl)
+{
+	struct source_impl *source, *tmp;
+	spa_list_for_each_safe(source, tmp, &impl->destroy_list, link)
+		free(source);
+	spa_list_init(&impl->destroy_list);
+}
+
 static int loop_iterate(void *object, int timeout)
 {
 	struct impl *impl = object;
@@ -354,11 +363,14 @@ static int loop_iterate(void *object, int timeout)
 	}
 	for (i = 0; i < nfds; i++) {
 		struct spa_source *s = ep[i].data;
-		if (SPA_LIKELY(s && s->rmask)) {
+		if (SPA_LIKELY(s && s->rmask && s->loop)) {
 			s->priv = NULL;
 			s->func(s);
 		}
 	}
+	if (SPA_UNLIKELY(!spa_list_is_empty(&impl->destroy_list)))
+		process_destroy(impl);
+
 	return nfds;
 }
 
@@ -712,7 +724,7 @@ static void loop_destroy_source(void *object, struct spa_source *source)
 		spa_system_close(impl->impl->system, source->fd);
 		source->fd = -1;
 	}
-	free(source);
+	spa_list_insert(&impl->impl->destroy_list, &impl->link);
 }
 
 static const struct spa_loop_methods impl_loop = {
@@ -783,6 +795,8 @@ static int impl_clear(struct spa_handle *handle)
 	spa_list_consume(source, &impl->source_list, link)
 		loop_destroy_source(impl, &source->source);
 
+	process_destroy(impl);
+
 	spa_system_close(impl->system, impl->ack_fd);
 	spa_system_close(impl->system, impl->poll_fd);
 
@@ -844,6 +858,7 @@ impl_init(const struct spa_handle_factory *factory,
 	impl->poll_fd = res;
 
 	spa_list_init(&impl->source_list);
+	spa_list_init(&impl->destroy_list);
 	spa_hook_list_init(&impl->hooks_list);
 
 	impl->buffer_data = SPA_PTR_ALIGN(impl->buffer_mem, MAX_ALIGN, uint8_t);
-- 
2.35.1