linux-kernel - [PATCH v5 3/5] tracing/probes: Fix to update dynamic data counter if fetcharg uses it

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Message-Id: <168908494781.123124.8160245359962103684.stgit@devnote2>
Date:   Tue, 11 Jul 2023 23:15:48 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [PATCH v5 3/5] tracing/probes: Fix to update dynamic data counter if fetcharg uses it

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

Fix to update dynamic data counter ('dyndata') and max length ('maxlen')
only if the fetcharg uses the dynamic data. Also get out arg->dynamic
from unlikely(). This makes dynamic data address wrong if
process_fetch_insn() returns error on !arg->dynamic case.

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Link: https://lore.kernel.org/all/20230710233400.5aaf024e@gandalf.local.home/
Fixes: 9178412ddf5a ("tracing: probeevent: Return consumed bytes of dynamic area")
Cc: stable@...r.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 kernel/trace/trace_probe_tmpl.h |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index ed9d57c6b041..185da001f4c3 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -267,11 +267,13 @@ store_trace_args(void *data, struct trace_probe *tp, void *rec,
 		if (unlikely(arg->dynamic))
 			*dl = make_data_loc(maxlen, dyndata - base);
 		ret = process_fetch_insn(arg->code, rec, dl, base);
-		if (unlikely(ret < 0 && arg->dynamic)) {
-			*dl = make_data_loc(0, dyndata - base);
-		} else {
-			dyndata += ret;
-			maxlen -= ret;
+		if (arg->dynamic) {
+			if (unlikely(ret < 0)) {
+				*dl = make_data_loc(0, dyndata - base);
+			} else {
+				dyndata += ret;
+				maxlen -= ret;
+			}
 		}
 	}
 }