linux-kernel - [PATCH bpf-next 2/2] fprobe: Fix sparse warning for acccessing __rcu ftrace

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Message-Id: <164802093635.1732982.4938094876018890866.stgit@devnote2>
Date:   Wed, 23 Mar 2022 16:35:36 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        kernel-janitors@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next 2/2] fprobe: Fix sparse warning for acccessing __rcu ftrace_hash

Since ftrace_ops::local_hash::filter_hash field is an __rcu pointer,
we have to use rcu_access_pointer() to access it.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/trace/fprobe.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 63b2321b22a0..89d9f994ebb0 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -215,7 +215,7 @@ int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter
 	 * correctly calculate the total number of filtered symbols
 	 * from both filter and notfilter.
 	 */
-	hash = fp->ops.local_hash.filter_hash;
+	hash = rcu_access_pointer(fp->ops.local_hash.filter_hash);
 	if (WARN_ON_ONCE(!hash))
 		goto out;