4.19-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (VMware) rostedt@goodmis.org
commit 7c6ea35ef50810aa12ab26f21cb858d980881576 upstream.
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: stable@kernel.org Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback") Reviewed-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace_functions_graph.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/kernel/trace/trace_functions_graph.c +++ b/kernel/trace/trace_functions_graph.c @@ -188,15 +188,17 @@ int function_graph_enter(unsigned long r 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;