From: "Steven Rostedt (VMware)" <rost...@goodmis.org>
The function graph profiler uses the ret_stack to store the "subtime" and
reuse it by nested functions and also on the return. But the current logic
has the profiler callback called before the ret_stack is updated, and it is
just modifying the ret_stack that will later be allocated (it's just lucky
that the "subtime" is not touched when it is allocated).
This could also cause a crash if we are at the end of the ret_stack when
this happens.
By reversing the order of the allocating the ret_stack and then calling the
callbacks attached to a function being traced, the ret_stack entry is no
longer used before it is allocated.
Cc: sta...@kernel.org
Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace
return callback")
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org>
---
kernel/trace/trace_functions_graph.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/trace/trace_functions_graph.c
b/kernel/trace/trace_functions_graph.c
index 4f0d72ae6362..2561460d7baf 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -188,15 +188,17 @@ int function_graph_enter(unsigned long ret, unsigned long
func,
trace.func = func;
trace.depth = ++current->curr_ret_depth;
- /* Only trace if the calling function expects to */
- if (!ftrace_graph_entry(&trace))
- goto out;
-
if (ftrace_push_return_trace(ret, func,
frame_pointer, retp))
goto out;
+ /* Only trace if the calling function expects to */
+ if (!ftrace_graph_entry(&trace))
+ goto out_ret;
+
return 0;
+ out_ret:
+ current->curr_ret_stack--;
out:
current->curr_ret_depth--;
return -EBUSY;
--
2.19.1
