This is a note to let you know that I've just added the patch titled
rethook: Reject getting a rethook if RCU is not watching
to the 5.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rethook-reject-getting-a-rethook-if-rcu-is-not-watch.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d84842d07ec9fef86435fea7240f33ee9140fa47
Author: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Date: Wed Jun 8 01:11:12 2022 +0900
rethook: Reject getting a rethook if RCU is not watching
[ 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@xxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/165461827269.280167.7379263615545598958.stgit@devnote2
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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;
