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function-graph: always initialize task ret_stack

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On creating a new task while running the function graph tracer, if
we fail to allocate the ret_stack, and then fail the fork, the
code will free the parent ret_stack. This is because the child
duplicated the parent and currently points to the parent's ret_stack.

This patch always initializes the task's ret_stack to NULL.

[ Impact: prevent crash of parent on low memory during fork ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2009-06-02 16:51:55 -04:00 committed by Steven Rostedt
parent f7e8b616ed
commit 84047e360a
1 changed files with 4 additions and 2 deletions
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6
kernel/trace/ftrace.c
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@ -2738,6 +2738,9 @@ void unregister_ftrace_graph(void)
/* Allocate a return stack for newly created task */
void ftrace_graph_init_task(struct task_struct *t)
{
/* Make sure we do not use the parent ret_stack */
t->ret_stack = NULL;
if (atomic_read(&ftrace_graph_active)) {
struct ftrace_ret_stack *ret_stack;
@ -2753,8 +2756,7 @@ void ftrace_graph_init_task(struct task_struct *t)
/* make curr_ret_stack visable before we add the ret_stack */
smp_wmb();
t->ret_stack = ret_stack;
} else
t->ret_stack = NULL;
}
}
void ftrace_graph_exit_task(struct task_struct *t)