On Tue, Apr 09, 2024 at 08:46AM -0700, Kees Cook wrote:
[...]
> > + trace_new_exec(current, bprm);
> > +
>
> All other steps in this function have explicit comments about
> what/why/etc. Please add some kind of comment describing why the
> tracepoint is where it is, etc.
I beefed up the tracepoint documentation, and wrote a little paragraph
above where it's called to reinforce what we want.
[...]
> What about binfmt_misc, and binfmt_script? You may want bprm->interp
> too?
Good points. I'll make the below changes for v2:
diff --git a/fs/exec.c b/fs/exec.c
index ab778ae1fc06..472b9f7b40e8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1268,6 +1268,12 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
return retval;
+ /*
+ * This tracepoint marks the point before flushing the old exec where
+ * the current task is still unchanged, but errors are fatal (point of
+ * no return). The later "sched_process_exec" tracepoint is called after
+ * the current task has successfully switched to the new exec.
+ */
trace_new_exec(current, bprm);
/*
diff --git a/include/trace/events/task.h b/include/trace/events/task.h
index 8853dc44783d..623d9af777c1 100644
--- a/include/trace/events/task.h
+++ b/include/trace/events/task.h
@@ -61,8 +61,11 @@ TRACE_EVENT(task_rename,
* @task: pointer to the current task
* @bprm: pointer to linux_binprm used for new exec
*
- * Called before flushing the old exec, but at the point of no return during
- * switching to the new exec.
+ * Called before flushing the old exec, where @task is still unchanged, but at
+ * the point of no return during switching to the new exec. At the point it is
+ * called the exec will either succeed, or on failure terminate the task. Also
+ * see the "sched_process_exec" tracepoint, which is called right after @task
+ * has successfully switched to the new exec.
*/
TRACE_EVENT(new_exec,
@@ -71,19 +74,22 @@ TRACE_EVENT(new_exec,
TP_ARGS(task, bprm),
TP_STRUCT__entry(
+ __string( interp, bprm->interp )
__string( filename, bprm->filename )
__field( pid_t, pid )
__string( comm, task->comm )
),
TP_fast_assign(
+ __assign_str(interp, bprm->interp);
__assign_str(filename, bprm->filename);
__entry->pid = task->pid;
__assign_str(comm, task->comm);
),
- TP_printk("filename=%s pid=%d comm=%s",
- __get_str(filename), __entry->pid, __get_str(comm))
+ TP_printk("interp=%s filename=%s pid=%d comm=%s",
+ __get_str(interp), __get_str(filename),
+ __entry->pid, __get_str(comm))
);
#endif
