Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit f7e8b616 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

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: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 26c01624

kernel/fork.c

+4 −6
Original line number Diff line number Diff line
@@ -982,6 +982,8 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	if (!p)

		goto fork_out;



	ftrace_graph_init_task(p);



	rt_mutex_init_task(p);



#ifdef CONFIG_PROVE_LOCKING
@@ -1131,8 +1133,6 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
		}

	}



	ftrace_graph_init_task(p);



	p->pid = pid_nr(pid);

	p->tgid = p->pid;

	if (clone_flags & CLONE_THREAD)
@@ -1141,7 +1141,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	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 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
		spin_unlock(&current->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 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	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);