function-graph: move initialization of new tasks up in fork
When the function graph tracer is enabled, all new tasks must allocate
a ret_stack to place the return address of functions. This is because
the function graph tracer will replace the real return address with a
call to the tracing of the exit function.
This initialization happens in fork, but it happens too late. If fork
fails, then it will call free_task and that calls the freeing of this
ret_stack. But before initialization happens, the new (failed) task
points to its parents ret_stack. If a fork failure happens during
the function trace, it would be catastrophic for the parent.
Also, there's no need to call ftrace_graph_exit_task from fork, since
it is called by free_task which fork calls on failure.
[ Impact: prevent crash during failed fork running function graph tracer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index b9e2edd..c4b1e35 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -982,6 +982,8 @@
if (!p)
goto fork_out;
+ ftrace_graph_init_task(p);
+
rt_mutex_init_task(p);
#ifdef CONFIG_PROVE_LOCKING
@@ -1131,8 +1133,6 @@
}
}
- ftrace_graph_init_task(p);
-
p->pid = pid_nr(pid);
p->tgid = p->pid;
if (clone_flags & CLONE_THREAD)
@@ -1141,7 +1141,7 @@
if (current->nsproxy != p->nsproxy) {
retval = ns_cgroup_clone(p, pid);
if (retval)
- goto bad_fork_free_graph;
+ goto bad_fork_free_pid;
}
p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
@@ -1233,7 +1233,7 @@
spin_unlock(¤t->sighand->siglock);
write_unlock_irq(&tasklist_lock);
retval = -ERESTARTNOINTR;
- goto bad_fork_free_graph;
+ goto bad_fork_free_pid;
}
if (clone_flags & CLONE_THREAD) {
@@ -1268,8 +1268,6 @@
cgroup_post_fork(p);
return p;
-bad_fork_free_graph:
- ftrace_graph_exit_task(p);
bad_fork_free_pid:
if (pid != &init_struct_pid)
free_pid(pid);