This is a note to let you know that I've just added the patch titled
tracing/kprobes: Check whether get_kretprobe() returns NULL in kretprobe_dispatcher()
to the 5.15-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:
tracing-kprobes-check-whether-get_kretprobe-returns-null-in-kretprobe_dispatcher.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From cc72b72073ac982a954d3b43519ca1c28f03c27c Mon Sep 17 00:00:00 2001
From: "Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx>
Date: Sat, 28 May 2022 00:55:39 +0900
Subject: tracing/kprobes: Check whether get_kretprobe() returns NULL in kretprobe_dispatcher()
From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
commit cc72b72073ac982a954d3b43519ca1c28f03c27c upstream.
There is a small chance that get_kretprobe(ri) returns NULL in
kretprobe_dispatcher() when another CPU unregisters the kretprobe
right after __kretprobe_trampoline_handler().
To avoid this issue, kretprobe_dispatcher() checks the get_kretprobe()
return value again. And if it is NULL, it returns soon because that
kretprobe is under unregistering process.
This issue has been introduced when the kretprobe is decoupled
from the struct kretprobe_instance by commit d741bf41d7c7
("kprobes: Remove kretprobe hash"). Before that commit, the
struct kretprob_instance::rp directly points the kretprobe
and it is never be NULL.
Link: https://lkml.kernel.org/r/165366693881.797669.16926184644089588731.stgit@devnote2
Reported-by: Yonghong Song <yhs@xxxxxx>
Fixes: d741bf41d7c7 ("kprobes: Remove kretprobe hash")
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: bpf <bpf@xxxxxxxxxxxxxxx>
Cc: Kernel Team <kernel-team@xxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace_kprobe.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1733,8 +1733,17 @@ static int
kretprobe_dispatcher(struct kretprobe_instance *ri, struct pt_regs *regs)
{
struct kretprobe *rp = get_kretprobe(ri);
- struct trace_kprobe *tk = container_of(rp, struct trace_kprobe, rp);
+ struct trace_kprobe *tk;
+ /*
+ * There is a small chance that get_kretprobe(ri) returns NULL when
+ * the kretprobe is unregister on another CPU between kretprobe's
+ * trampoline_handler and this function.
+ */
+ if (unlikely(!rp))
+ return 0;
+
+ tk = container_of(rp, struct trace_kprobe, rp);
raw_cpu_inc(*tk->nhit);
if (trace_probe_test_flag(&tk->tp, TP_FLAG_TRACE))
Patches currently in stable-queue which might be from mhiramat@xxxxxxxxxx are
queue-5.15/tracing-kprobes-check-whether-get_kretprobe-returns-null-in-kretprobe_dispatcher.patch
