linux-kernel - [PATCH 1/2] ftrace: Update ftrace_ops->next pointer with rcu_assign

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Message-ID: <20210317102529.226734-2-lihuafei1@huawei.com>
Date:   Wed, 17 Mar 2021 18:25:28 +0800
From:   Li Huafei <lihuafei1@...wei.com>
To:     <rostedt@...dmis.org>, <mingo@...hat.com>, <jolsa@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <yangjihong1@...wei.com>,
        <xukuohai@...wei.com>, <zhangjinhao2@...wei.com>,
        <lihuafei1@...wei.com>
Subject: [PATCH 1/2] ftrace: Update ftrace_ops->next pointer with rcu_assign_pointer()

The unregistered ftrace_ops may be freed by the caller, so we should use
rcu_assign_pointer() in remove_ftrace_ops() to remove the ftrace_ops,
which ensures that no more users will reference the ftrace_ops after
synchronize_rcu() is called.

Signed-off-by: Li Huafei <lihuafei1@...wei.com>
---
 kernel/trace/ftrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 4d8e35575549..2e315a145d20 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -282,7 +282,7 @@ static int remove_ftrace_ops(struct ftrace_ops __rcu **list,
 			lockdep_is_held(&ftrace_lock)) == ops &&
 	    rcu_dereference_protected(ops->next,
 			lockdep_is_held(&ftrace_lock)) == &ftrace_list_end) {
-		*list = &ftrace_list_end;
+		rcu_assign_pointer(*list, &ftrace_list_end);
 		return 0;
 	}
 
@@ -293,7 +293,7 @@ static int remove_ftrace_ops(struct ftrace_ops __rcu **list,
 	if (*p != ops)
 		return -1;
 
-	*p = (*p)->next;
+	rcu_assign_pointer(*p, (*p)->next);
 	return 0;
 }
 
-- 
2.17.1