From 172c8add7dfae2853debe9cd70e41d736059e978 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Chlo=C3=A9=20Vulquin?= Date: Thu, 28 Mar 2024 13:46:20 +0100 Subject: [PATCH] xcursor: catch theme inheritance loops MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit As of currently, when an xcursor theme depends on itself or another theme that will eventually depend on it, `xcursor_load_theme` will recurse infinitely while processing the inherits. This change introduces a stack-allocated linked list of visited nodes by name, and skips any already visited nodes in the inherit list. Side effects: * Since the linked list is stack-allocated, there is a potential for an overflow if there is a very long list of dependencies. If this turns out to be a legitimate concern, the linked list is trivial to convert to being heap-allocated. * There is an existing linked list (technically doubly linked list) implementation in the wayland codebase. As of currently, the xcursor codebase does not refer to it. Consequently, this change writes a minimal single linked list implementation to utilize directly. This changeset is based on the merge request in wayland/wayland!376. The xcursor code is mostly shared between the two. This changeset diverges the files slightly due to stylistic differences between the repositories, but the logic is identical. Signed-off-by: Chloé Vulquin --- xcursor/xcursor.c | 86 +++++++++++++++++++++++++++++++++-------------- 1 file changed, 61 insertions(+), 25 deletions(-) diff --git a/xcursor/xcursor.c b/xcursor/xcursor.c index 663467097..b5edb9de8 100644 --- a/xcursor/xcursor.c +++ b/xcursor/xcursor.c @@ -723,38 +723,44 @@ load_all_cursors_from_dir(const char *path, int size, closedir(dir); } -/** Load all the cursor of a theme - * - * This function loads all the cursor images of a given theme and its - * inherited themes. Each cursor is loaded into an struct xcursor_images object - * which is passed to the caller's load callback. If a cursor appears - * more than once across all the inherited themes, the load callback - * will be called multiple times, with possibly different struct xcursor_images - * object which have the same name. The user is expected to destroy the - * struct xcursor_images objects passed to the callback with - * xcursor_images_destroy(). - * - * \param theme The name of theme that should be loaded - * \param size The desired size of the cursor images - * \param load_callback A callback function that will be called - * for each cursor loaded. The first parameter is the struct xcursor_images - * object representing the loaded cursor and the second is a pointer - * to data provided by the user. - * \param user_data The data that should be passed to the load callback - */ -void -xcursor_load_theme(const char *theme, int size, - void (*load_callback)(struct xcursor_images *, void *), - void *user_data) +struct xcursor_nodelist { + size_t nodelen; + const char *node; + struct xcursor_nodelist *next; +}; + +static bool +nodelist_contains(struct xcursor_nodelist *nodelist, const char *s, size_t ss) { + struct xcursor_nodelist *vi; + for (vi = nodelist; vi && vi->node; vi = vi->next) { + if (vi->nodelen == ss && !strncmp(s, vi->node, vi->nodelen)) + return true; + } + return false; +} + +static void +xcursor_load_theme_protected(const char *theme, + int size, + void (*load_callback)(struct xcursor_images *, void *), + void *user_data, + struct xcursor_nodelist *visited_nodes) { char *full, *dir; char *inherits = NULL; const char *path, *i; char *xcursor_path; + size_t si; + struct xcursor_nodelist current_node; if (!theme) theme = "default"; + current_node.next = visited_nodes; + current_node.node = theme; + current_node.nodelen = strlen(theme); + visited_nodes = ¤t_node; + xcursor_path = xcursor_library_path(); for (path = xcursor_path; path; @@ -779,9 +785,39 @@ xcursor_load_theme(const char *theme, int size, free(dir); } - for (i = inherits; i; i = xcursor_next_path(i)) - xcursor_load_theme(i, size, load_callback, user_data); + for (i = inherits; i; i = xcursor_next_path(i)) { + si = strlen(i); + if (nodelist_contains(visited_nodes, i, si)) + continue; + xcursor_load_theme_protected(i, size, load_callback, user_data, visited_nodes); + } free(inherits); free(xcursor_path); } + +/** Load all the cursor of a theme + * + * This function loads all the cursor images of a given theme and its + * inherited themes. Each cursor is loaded into an struct xcursor_images object + * which is passed to the caller's load callback. If a cursor appears + * more than once across all the inherited themes, the load callback + * will be called multiple times, with possibly different struct xcursor_images + * object which have the same name. The user is expected to destroy the + * struct xcursor_images objects passed to the callback with + * xcursor_images_destroy(). + * + * \param theme The name of theme that should be loaded + * \param size The desired size of the cursor images + * \param load_callback A callback function that will be called + * for each cursor loaded. The first parameter is the struct xcursor_images + * object representing the loaded cursor and the second is a pointer + * to data provided by the user. + * \param user_data The data that should be passed to the load callback + */ +void +xcursor_load_theme(const char *theme, int size, + void (*load_callback)(struct xcursor_images *, void *), + void *user_data) { + return xcursor_load_theme_protected(theme, size, load_callback, user_data, NULL); +}