6.6-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt rostedt@goodmis.org
commit 6f86bdeab633a56d5c6dccf1a2c5989b6a5e323e upstream.
The following commands causes a crash:
~# cd /sys/kernel/tracing/events/rcu/rcu_callback ~# echo 'hist:name=bad:keys=common_pid:onmax(bogus).save(common_pid)' > trigger bash: echo: write error: Invalid argument ~# echo 'hist:name=bad:keys=common_pid' > trigger
Because the following occurs:
event_trigger_write() { trigger_process_regex() { event_hist_trigger_parse() {
data = event_trigger_alloc(..);
event_trigger_register(.., data) { cmd_ops->reg(.., data, ..) [hist_register_trigger()] { data->ops->init() [event_hist_trigger_init()] { save_named_trigger(name, data) { list_add(&data->named_list, &named_triggers); } } } }
ret = create_actions(); (return -EINVAL) if (ret) goto out_unreg; [..] ret = hist_trigger_enable(data, ...) { list_add_tail_rcu(&data->list, &file->triggers); <<<---- SKIPPED!!! (this is important!) [..] out_unreg: event_hist_unregister(.., data) { cmd_ops->unreg(.., data, ..) [hist_unregister_trigger()] { list_for_each_entry(iter, &file->triggers, list) { if (!hist_trigger_match(data, iter, named_data, false)) <- never matches continue; [..] test = iter; } if (test && test->ops->free) <<<-- test is NULL
test->ops->free(test) [event_hist_trigger_free()] { [..] if (data->name) del_named_trigger(data) { list_del(&data->named_list); <<<<-- NEVER gets removed! } } } }
[..] kfree(data); <<<-- frees item but it is still on list
The next time a hist with name is registered, it causes an u-a-f bug and the kernel can crash.
Move the code around such that if event_trigger_register() succeeds, the next thing called is hist_trigger_enable() which adds it to the list.
A bunch of actions is called if get_named_trigger_data() returns false. But that doesn't need to be called after event_trigger_register(), so it can be moved up, allowing event_trigger_register() to be called just before hist_trigger_enable() keeping them together and allowing the file->triggers to be properly populated.
Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Link: https://lore.kernel.org/20250227163944.1c37f85f@gandalf.local.home Fixes: 067fe038e70f6 ("tracing: Add variable reference handling to hist triggers") Reported-by: Tomas Glozar tglozar@redhat.com Tested-by: Tomas Glozar tglozar@redhat.com Reviewed-by: Tom Zanussi zanussi@kernel.org Closes: https://lore.kernel.org/all/CAP4=nvTsxjckSBTz=Oe_UYh8keD9_sZC4i++4h72mJLic4_... Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace_events_hist.c | 30 +++++++++++++++--------------- 1 file changed, 15 insertions(+), 15 deletions(-)
--- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -6660,27 +6660,27 @@ static int event_hist_trigger_parse(stru if (existing_hist_update_only(glob, trigger_data, file)) goto out_free;
- ret = event_trigger_register(cmd_ops, file, glob, trigger_data); - if (ret < 0) - goto out_free; + if (!get_named_trigger_data(trigger_data)) {
- if (get_named_trigger_data(trigger_data)) - goto enable; + ret = create_actions(hist_data); + if (ret) + goto out_free;
- ret = create_actions(hist_data); - if (ret) - goto out_unreg; + if (has_hist_vars(hist_data) || hist_data->n_var_refs) { + ret = save_hist_vars(hist_data); + if (ret) + goto out_free; + }
- if (has_hist_vars(hist_data) || hist_data->n_var_refs) { - ret = save_hist_vars(hist_data); + ret = tracing_map_init(hist_data->map); if (ret) - goto out_unreg; + goto out_free; }
- ret = tracing_map_init(hist_data->map); - if (ret) - goto out_unreg; -enable: + ret = event_trigger_register(cmd_ops, file, glob, trigger_data); + if (ret < 0) + goto out_free; + ret = hist_trigger_enable(trigger_data, file); if (ret) goto out_unreg;