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Commit 84047e36 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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function-graph: always initialize task ret_stack 



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: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f7e8b616

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)