[PATCH 2/2] function-graph: always initialize task ret_stack
- From: Steven Rostedt <rostedt@xxxxxxxxxxx>
- Date: Tue, 02 Jun 2009 18:02:14 -0400
From: Steven Rostedt <srostedt@xxxxxxxxxx>
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@xxxxxxxxxxx>
---
kernel/trace/ftrace.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1664d3f..bb081f3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -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)
--
1.6.3.1
--
--
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- References:
- [PATCH 0/2] [GIT PULL][urgent] function-graph: allocation and freeing of ret_stack
- From: Steven Rostedt
- [PATCH 0/2] [GIT PULL][urgent] function-graph: allocation and freeing of ret_stack
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