ftrace: Fix issue that 'direct->addr' not restored in modify_ftrace_direct()

Syzkaller report a WARNING: "WARN_ON(!direct)" in modify_ftrace_direct().

Root cause is 'direct->addr' was changed from 'old_addr' to 'new_addr' but
not restored if error happened on calling ftrace_modify_direct_caller().
Then it can no longer find 'direct' by that 'old_addr'.

To fix it, restore 'direct->addr' to 'old_addr' explicitly in error path.

Link: https://lore.kernel.org/linux-trace-kernel/20230330025223.1046087-1-zhengyejian1@huawei.com
Cc: stable@vger.kernel.org
Cc: <mhiramat@kernel.org>
Cc: <mark.rutland@arm.com>
Cc: <ast@kernel.org>
Cc: <daniel@iogearbox.net>
Fixes: 8a141dd7f706 ("ftrace: Fix modify_ftrace_direct.")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0feea145bb2995e17ef79cad1596867be5f8caca..c67bcc89a77168cd9d9d7db3e0381db4ebdb86b7 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5667,12 +5667,15 @@ int modify_ftrace_direct(unsigned long ip,
                ret = 0;
        }
 
-       if (unlikely(ret && new_direct)) {
-               direct->count++;
-               list_del_rcu(&new_direct->next);
-               synchronize_rcu_tasks();
-               kfree(new_direct);
-               ftrace_direct_func_count--;
+       if (ret) {
+               direct->addr = old_addr;
+               if (unlikely(new_direct)) {
+                       direct->count++;
+                       list_del_rcu(&new_direct->next);
+                       synchronize_rcu_tasks();
+                       kfree(new_direct);
+                       ftrace_direct_func_count--;
+               }
        }
 
  out_unlock: