From 2eebf802dd2bd192e30d2acca9779821d35da967 Mon Sep 17 00:00:00 2001 From: Zephyr Lykos Date: Wed, 27 Sep 2023 16:31:55 +0800 Subject: [PATCH] gthreadedresolver: Fix race between source callbacks and finalize (fedora#2235890) --- glib2.spec | 4 ++ gthreadedresolver-race.patch | 132 +++++++++++++++++++++++++++++++++++ 2 files changed, 136 insertions(+) create mode 100644 gthreadedresolver-race.patch diff --git a/glib2.spec b/glib2.spec index 024b513..50c25c6 100644 --- a/glib2.spec +++ b/glib2.spec @@ -16,6 +16,10 @@ Patch: gnutls-hmac.patch # the baremetal Docker is updated there i.e. lets be a little bit pragmatic... Patch: gspawn-eperm.patch +# https://gitlab.gnome.org/GNOME/glib/-/merge_requests/3575 +# not released yet +Patch: gthreadedresolver-race.patch + BuildRequires: gcc BuildRequires: gcc-c++ BuildRequires: gettext diff --git a/gthreadedresolver-race.patch b/gthreadedresolver-race.patch new file mode 100644 index 0000000..911b78c --- /dev/null +++ b/gthreadedresolver-race.patch @@ -0,0 +1,132 @@ +From 82c764ce2e42f0d1032627dabcbd742d5f2bd8fa Mon Sep 17 00:00:00 2001 +From: Philip Withnall +Date: Mon, 11 Sep 2023 16:02:15 +0100 +Subject: [PATCH] gthreadedresolver: Fix race between source callbacks and + finalize +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +I had thought that because `g_source_destroy()` was called for the two +sources (cancel and timeout) in the `GTask` finalize function for a +threaded resolver operation, that it would be fine to use a plain +pointer in the source callbacks to point to the `GTask`. + +That turns out to not be true: because the source callbacks are executed +in the GLib worker thread, and the `GTask` can be finalized in another +thread, it’s possible for a source callback (e.g. `cancelled_cb()`) to +be scheduled in the worker thread, then for the `GTask` to be finalized, +and then the source callback to continue execution and find itself +doing a use-after-free. + +Fix that by using a weak ref to the `GTask` in the source callbacks, +rather than a plain pointer. + +Signed-off-by: Philip Withnall + +Fixes: #3105 +--- + gio/gthreadedresolver.c | 43 +++++++++++++++++++++++++++++++++++------ + 1 file changed, 37 insertions(+), 6 deletions(-) + +diff --git a/gio/gthreadedresolver.c b/gio/gthreadedresolver.c +index 2d94531bfd..c7a567549f 100644 +--- a/gio/gthreadedresolver.c ++++ b/gio/gthreadedresolver.c +@@ -1422,10 +1422,17 @@ lookup_records_finish (GResolver *resolver, + static gboolean + timeout_cb (gpointer user_data) + { +- GTask *task = G_TASK (user_data); +- LookupData *data = g_task_get_task_data (task); ++ GWeakRef *weak_task = user_data; ++ GTask *task = NULL; /* (owned) */ ++ LookupData *data; + gboolean should_return; + ++ task = g_weak_ref_get (weak_task); ++ if (task == NULL) ++ return G_SOURCE_REMOVE; ++ ++ data = g_task_get_task_data (task); ++ + g_mutex_lock (&data->lock); + + should_return = g_atomic_int_compare_and_exchange (&data->will_return, NOT_YET, TIMED_OUT); +@@ -1443,6 +1450,8 @@ timeout_cb (gpointer user_data) + g_cond_broadcast (&data->cond); + g_mutex_unlock (&data->lock); + ++ g_object_unref (task); ++ + return G_SOURCE_REMOVE; + } + +@@ -1452,10 +1461,17 @@ static gboolean + cancelled_cb (GCancellable *cancellable, + gpointer user_data) + { +- GTask *task = G_TASK (user_data); +- LookupData *data = g_task_get_task_data (task); ++ GWeakRef *weak_task = user_data; ++ GTask *task = NULL; /* (owned) */ ++ LookupData *data; + gboolean should_return; + ++ task = g_weak_ref_get (weak_task); ++ if (task == NULL) ++ return G_SOURCE_REMOVE; ++ ++ data = g_task_get_task_data (task); ++ + g_mutex_lock (&data->lock); + + g_assert (g_cancellable_is_cancelled (cancellable)); +@@ -1473,9 +1489,18 @@ cancelled_cb (GCancellable *cancellable, + g_cond_broadcast (&data->cond); + g_mutex_unlock (&data->lock); + ++ g_object_unref (task); ++ + return G_SOURCE_REMOVE; + } + ++static void ++weak_ref_clear_and_free (GWeakRef *weak_ref) ++{ ++ g_weak_ref_clear (weak_ref); ++ g_free (weak_ref); ++} ++ + static void + run_task_in_thread_pool_async (GThreadedResolver *self, + GTask *task) +@@ -1490,17 +1515,23 @@ run_task_in_thread_pool_async (GThreadedResolver *self, + + if (timeout_ms != 0) + { ++ GWeakRef *weak_task = g_new0 (GWeakRef, 1); ++ g_weak_ref_set (weak_task, task); ++ + data->timeout_source = g_timeout_source_new (timeout_ms); + g_source_set_static_name (data->timeout_source, "[gio] threaded resolver timeout"); +- g_source_set_callback (data->timeout_source, G_SOURCE_FUNC (timeout_cb), task, NULL); ++ g_source_set_callback (data->timeout_source, G_SOURCE_FUNC (timeout_cb), g_steal_pointer (&weak_task), (GDestroyNotify) weak_ref_clear_and_free); + g_source_attach (data->timeout_source, GLIB_PRIVATE_CALL (g_get_worker_context) ()); + } + + if (cancellable != NULL) + { ++ GWeakRef *weak_task = g_new0 (GWeakRef, 1); ++ g_weak_ref_set (weak_task, task); ++ + data->cancellable_source = g_cancellable_source_new (cancellable); + g_source_set_static_name (data->cancellable_source, "[gio] threaded resolver cancellable"); +- g_source_set_callback (data->cancellable_source, G_SOURCE_FUNC (cancelled_cb), task, NULL); ++ g_source_set_callback (data->cancellable_source, G_SOURCE_FUNC (cancelled_cb), g_steal_pointer (&weak_task), (GDestroyNotify) weak_ref_clear_and_free); + g_source_attach (data->cancellable_source, GLIB_PRIVATE_CALL (g_get_worker_context) ()); + } + +-- +GitLab +