function-graph: always initialize task ret_stack (84047e36) · Commits · 戴 / test

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>

kernel/trace/ftrace.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -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)

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