From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Jiri Olsa <jolsa@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
bpf@vger.kernel.org
Subject: [PATCH bpf v2 2/2] rethook: Reject getting a rethook if RCU is not watching
Date: Wed, 8 Jun 2022 01:11:12 +0900 [thread overview]
Message-ID: <165461827269.280167.7379263615545598958.stgit@devnote2> (raw)
In-Reply-To: <165461825202.280167.12903689442217921817.stgit@devnote2>
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Since the rethook_recycle() will involve the call_rcu() for reclaiming
the rethook_instance, the rethook must be set up at the RCU available
context (non idle). This rethook_recycle() in the rethook trampoline
handler is inevitable, thus the RCU available check must be done before
setting the rethook trampoline.
This adds a rcu_is_watching() check in the rethook_try_get() so that
it will return NULL if it is called when !rcu_is_watching().
Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
kernel/trace/rethook.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
index b56833700d23..c69d82273ce7 100644
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -154,6 +154,15 @@ struct rethook_node *rethook_try_get(struct rethook *rh)
if (unlikely(!handler))
return NULL;
+ /*
+ * This expects the caller will set up a rethook on a function entry.
+ * When the function returns, the rethook will eventually be reclaimed
+ * or released in the rethook_recycle() with call_rcu().
+ * This means the caller must be run in the RCU-availabe context.
+ */
+ if (unlikely(!rcu_is_watching()))
+ return NULL;
+
fn = freelist_try_get(&rh->pool);
if (!fn)
return NULL;
next prev parent reply other threads:[~2022-06-07 16:11 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-07 16:10 [PATCH bpf v2 0/2] rethook: Reject getting a rethook if RCU is not watching Masami Hiramatsu (Google)
2022-06-07 16:11 ` [PATCH bpf v2 1/2] fprobe: samples: Add use_trace option and show hit/missed counter Masami Hiramatsu (Google)
2022-06-17 16:06 ` Steven Rostedt
2022-06-22 1:41 ` Masami Hiramatsu
2022-06-07 16:11 ` Masami Hiramatsu (Google) [this message]
2022-06-17 16:19 ` [PATCH bpf v2 2/2] rethook: Reject getting a rethook if RCU is not watching Steven Rostedt
2022-06-17 11:27 ` [PATCH bpf v2 0/2] " Jiri Olsa
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