From: Masami Hiramatsu (Google) mhiramat@kernel.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@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Steven Rostedt (Google) rostedt@goodmis.org Acked-by: Jiri Olsa jolsa@kernel.org Link: https://lore.kernel.org/bpf/165461827269.280167.7379263615545598958.stgit@de... Signed-off-by: Sasha Levin sashal@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;