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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2017-08-17 16:37:25 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-30 10:21:50 +0200
commit741397d16a3d65e1629e9be75f5d64687d767664 (patch)
tree9e083e5df349b67965e1041268b3c6f4ad9fae40
parentfd8235e721ef8bb15ba390d9f2f806f794368536 (diff)
ftrace: Check for null ret_stack on profile function graph entry function
commit a8f0f9e49956a74718874b800251455680085600 upstream. There's a small race when function graph shutsdown and the calling of the registered function graph entry callback. The callback must not reference the task's ret_stack without first checking that it is not NULL. Note, when a ret_stack is allocated for a task, it stays allocated until the task exits. The problem here, is that function_graph is shutdown, and a new task was created, which doesn't have its ret_stack allocated. But since some of the functions are still being traced, the callbacks can still be called. The normal function_graph code handles this, but starting with commit 8861dd303c ("ftrace: Access ret_stack->subtime only in the function profiler") the profiler code references the ret_stack on function entry, but doesn't check if it is NULL first. Link: https://bugzilla.kernel.org/show_bug.cgi?id=196611 Fixes: 8861dd303c ("ftrace: Access ret_stack->subtime only in the function profiler") Reported-by: lilydjwg@gmail.com Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/trace/ftrace.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4f7ea8446bb5..6e432ed7d0fe 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -876,6 +876,10 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace)
function_profile_call(trace->func, 0, NULL, NULL);
+ /* If function graph is shutting down, ret_stack can be NULL */
+ if (!current->ret_stack)
+ return 0;
+
if (index >= 0 && index < FTRACE_RETFUNC_DEPTH)
current->ret_stack[index].subtime = 0;