From 1a7e69fced4637d47b1a92817a53f942382527ff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Florian=20M=C3=BCllner?= <fmuellner@redhat.com>
Date: Wed, 29 Jan 2025 14:22:20 +0100
Subject: [PATCH] Fix refcount issue in stylesheet tracking

Resolves: https://issues.redhat.com/browse/RHEL-62870
---
 ...-theme-Reuse-stylesheets-if-possible.patch | 114 ++++++++++++++++++
 gnome-shell.spec                              |   1 +
 2 files changed, 115 insertions(+)
 create mode 100644 0001-st-theme-Reuse-stylesheets-if-possible.patch

diff --git a/0001-st-theme-Reuse-stylesheets-if-possible.patch b/0001-st-theme-Reuse-stylesheets-if-possible.patch
new file mode 100644
index 0000000..f608a92
--- /dev/null
+++ b/0001-st-theme-Reuse-stylesheets-if-possible.patch
@@ -0,0 +1,114 @@
+From 4ad7120d0188dcf21146da02637f82bac2ac7ad6 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Florian=20M=C3=BCllner?= <fmuellner@gnome.org>
+Date: Wed, 29 Jan 2025 02:46:44 +0100
+Subject: [PATCH] st/theme: Reuse stylesheets if possible
+
+The following happens when processing an `@import()` rule:
+
+ 1. `_st_theme_resolve_url()` to resolve file
+ 2. `insert_stylesheet()` to track file/sheet
+   a. take ownership of file/sheet (ref)
+   b. use file as key in `stylesheets_by_file` hash table
+   c. use file as value in `files_by_stylesheet` hash table
+ 3. release reference to file
+
+This leads to a refcount error when importing a file that
+was already parsed before:
+
+ 1. file start with refcount 1
+ 2. `insert_stylesheet()`
+   a. increases refcount to 2
+   b. inserting into `stylesheets_by_file` *decreases* the
+      passed-in key if the key already exists
+   c. `files_by_stylesheet` now tracks a file with recount 1
+ 3. releases the last reference to file
+
+The file object tracked in `files_by_stylesheet` is now invalid,
+and accessing it results in a crash.
+
+Avoid this issue by reusing existing stylesheets, so we don't insert
+a stylesheet that's already tracked.
+
+As a side-effect, this also saves us from re-parsing the same file
+unnecessarily.
+
+Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7306
+---
+ src/st/st-theme.c | 32 ++++++++++++++++++++++++++------
+ 1 file changed, 26 insertions(+), 6 deletions(-)
+
+diff --git a/src/st/st-theme.c b/src/st/st-theme.c
+index 9867ee1510..9ad99e2b1a 100644
+--- a/src/st/st-theme.c
++++ b/src/st/st-theme.c
+@@ -244,6 +244,27 @@ insert_stylesheet (StTheme      *theme,
+   g_hash_table_insert (theme->files_by_stylesheet, stylesheet, file);
+ }
+ 
++static CRStyleSheet *
++resolve_stylesheet (StTheme  *theme,
++                    GFile    *file,
++                    GError  **error)
++{
++  CRStyleSheet *sheet;
++
++  sheet = g_hash_table_lookup (theme->stylesheets_by_file, file);
++  if (sheet)
++    {
++      cr_stylesheet_ref (sheet);
++      return sheet;
++    }
++
++  sheet = parse_stylesheet (file, error);
++  if (sheet)
++    insert_stylesheet (theme, file, sheet);
++
++  return sheet;
++}
++
+ /**
+  * st_theme_load_stylesheet:
+  * @theme: a #StTheme
+@@ -261,13 +282,12 @@ st_theme_load_stylesheet (StTheme    *theme,
+ {
+   CRStyleSheet *stylesheet;
+ 
+-  stylesheet = parse_stylesheet (file, error);
++  stylesheet = resolve_stylesheet (theme, file, error);
+   if (!stylesheet)
+     return FALSE;
+ 
+   stylesheet->app_data = GUINT_TO_POINTER (TRUE);
+ 
+-  insert_stylesheet (theme, file, stylesheet);
+   cr_stylesheet_ref (stylesheet);
+   theme->custom_stylesheets = g_slist_prepend (theme->custom_stylesheets, stylesheet);
+   g_signal_emit (theme, signals[STYLESHEETS_CHANGED], 0);
+@@ -884,6 +904,7 @@ add_matched_properties (StTheme      *a_this,
+ 
+             if (import_rule->sheet == NULL)
+               {
++                CRStyleSheet *sheet = NULL;
+                 GFile *file = NULL;
+ 
+                 if (import_rule->url->stryng && import_rule->url->stryng->str)
+@@ -891,13 +912,12 @@ add_matched_properties (StTheme      *a_this,
+                     file = _st_theme_resolve_url (a_this,
+                                                   a_nodesheet,
+                                                   import_rule->url->stryng->str);
+-                    import_rule->sheet = parse_stylesheet (file, NULL);
++                    sheet = resolve_stylesheet (a_this, file, NULL);
+                   }
+ 
+-                if (import_rule->sheet)
++                if (sheet)
+                   {
+-                    insert_stylesheet (a_this, file, import_rule->sheet);
+-                    /* refcount of stylesheets starts off at zero, so we don't need to unref! */
++                    import_rule->sheet = sheet;
+                   }
+                 else
+                   {
+-- 
+2.48.1
+
diff --git a/gnome-shell.spec b/gnome-shell.spec
index be6041e..dc782a4 100644
--- a/gnome-shell.spec
+++ b/gnome-shell.spec
@@ -43,6 +43,7 @@ Patch: 0001-st-texture-cache-purge-on-resume.patch
 Patch: fix-some-js-warnings.patch
 Patch: 0001-data-Update-generated-stylesheets.patch
 Patch: 0001-theme-Welcome-Illustration.patch
+Patch: 0001-st-theme-Reuse-stylesheets-if-possible.patch
 
 %define eds_version 3.45.1
 %define gnome_desktop_version 44.0-7