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Date: Mon, 27 Jun 2022 13:20:34 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, "Masami Hiramatsu (Google)" <mhiramat@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, "Steven Rostedt (Google)" <rostedt@...dmis.org>, Jiri Olsa <jolsa@...nel.org>, Sasha Levin <sashal@...nel.org> Subject: [PATCH 5.18 061/181] rethook: Reject getting a rethook if RCU is not watching From: Masami Hiramatsu (Google) <mhiramat@...nel.org> [ Upstream commit c0f3bb4054ef036e5f67e27f2e3cad9e6512cf00 ] 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@...nel.org> Signed-off-by: Daniel Borkmann <daniel@...earbox.net> Acked-by: Steven Rostedt (Google) <rostedt@...dmis.org> Acked-by: Jiri Olsa <jolsa@...nel.org> Link: https://lore.kernel.org/bpf/165461827269.280167.7379263615545598958.stgit@devnote2 Signed-off-by: Sasha Levin <sashal@...nel.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; -- 2.35.1
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