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function-graph: move initialization of new tasks up in fork

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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>
This commit is contained in:
Steven Rostedt 2009-06-02 16:39:48 -04:00 committed by Steven Rostedt
parent 26c01624a2
commit f7e8b616ed
1 changed files with 4 additions and 6 deletions
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10
kernel/fork.c
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@ -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);