livepatch: RCU protect struct klp_func all the time when used in klp_ftrace_handler()

func->new_func has been accessed after rcu_read_unlock() in klp_ftrace_handler()
and therefore the access was not protected.

Signed-off-by: Petr Mladek <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Signed-off-by: Jiri Kosina <[email protected]>

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 69bf3aa3bde8200b0a39665898c6cfeab8699cdb..782172f073c5ed4bde5318bf96777ee79c618b89 100644 (file)
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -314,12 +314,12 @@ static void notrace klp_ftrace_handler(unsigned long ip,
        rcu_read_lock();
        func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
                                      stack_node);
-       rcu_read_unlock();
-
        if (WARN_ON_ONCE(!func))
-               return;
+               goto unlock;
 
        klp_arch_set_pc(regs, (unsigned long)func->new_func);
+unlock:
+       rcu_read_unlock();
 }
 
 static int klp_disable_func(struct klp_func *func)