tracing: Fix free of probe entry by calling call_rcu_sched()

Because function tracing is very invasive, and can even trace
calls to rcu_read_lock(), RCU access in function tracing is done
with preempt_disable_notrace(). This requires a synchronize_sched()
for updates and not a synchronize_rcu().

Function probes (traceon, traceoff, etc) must be freed after
a synchronize_sched() after its entry has been removed from the
hash. But call_rcu() is used. Fix this by using call_rcu_sched().

Also fix the usage to use hlist_del_rcu() instead of hlist_del().

Cc: stable@vger.kernel.org
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 98ca94a41819..e6effd0c40a9 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3108,8 +3108,8 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
                                         continue;
                         }
 
-                        hlist_del(&entry->node);
-                        call_rcu(&entry->rcu, ftrace_free_entry_rcu);
+                        hlist_del_rcu(&entry->node);
+                        call_rcu_sched(&entry->rcu, ftrace_free_entry_rcu);
                 }
         }
         __disable_ftrace_function_probe();