linux-kernel - [PATCH v2] tracing/fprobe: Fix to check whether fprobe is registered correctly

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Message-Id: <166677683946.1459107.15997653945538644683.stgit@devnote3>
Date:   Wed, 26 Oct 2022 18:33:59 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Jiri Olsa <jolsa@...nel.org>
Subject: [PATCH v2] tracing/fprobe: Fix to check whether fprobe is registered correctly

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Since commit ab51e15d535e ("fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag
for fprobe") introduced fprobe_kprobe_handler() for fprobe::ops::func,
unregister_fprobe() fails to unregister the registered if user specifies
FPROBE_FL_KPROBE_SHARED flag.
Moreover, __register_ftrace_function() is possible to change the
ftrace_ops::func, thus we have to check fprobe::ops::saved_func instead.

To check it correctly, it should confirm the fprobe::ops::saved_func is
either fprobe_handler() or fprobe_kprobe_handler().

Fixes: cad9931f64dc ("fprobe: Add ftrace based probe APIs")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 kernel/trace/fprobe.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 71614b2a67ff..e8143e368074 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -303,7 +303,8 @@ int unregister_fprobe(struct fprobe *fp)
 {
 	int ret;

-	if (!fp || fp->ops.func != fprobe_handler)
+	if (!fp || (fp->ops.saved_func != fprobe_handler &&
+		    fp->ops.saved_func != fprobe_kprobe_handler))
 		return -EINVAL;

 	/*