linux-kernel - [PATCH v4 1/4] tracing/probes: Fix to avoid double count of the string length on the array

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Message-ID:  <168904148467.2908673.7907708071012864793.stgit@mhiramat.roam.corp.google.com>
Date:   Tue, 11 Jul 2023 11:11:24 +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 v4 1/4] tracing/probes: Fix to avoid double count of the string length on the array

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

If an array is specified with the ustring or symstr, the length of the
strings are accumlated on both of 'ret' and 'total', which means the
length is double counted.
Just set the length to the 'ret' value for avoiding double counting.

Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
Closes: https://lore.kernel.org/all/8819b154-2ba1-43c3-98a2-cbde20892023@moroto.mountain/
Fixes: 88903c464321 ("tracing/probe: Add ustring type for user-space string")
Cc: stable@...r.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
Changes in v2:
 - Fix patch description.
---
 kernel/trace/trace_probe_tmpl.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 00707630788d..4735c5cb76fa 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -156,11 +156,11 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
 			code++;
 			goto array;
 		case FETCH_OP_ST_USTRING:
-			ret += fetch_store_strlen_user(val + code->offset);
+			ret = fetch_store_strlen_user(val + code->offset);
 			code++;
 			goto array;
 		case FETCH_OP_ST_SYMSTR:
-			ret += fetch_store_symstrlen(val + code->offset);
+			ret = fetch_store_symstrlen(val + code->offset);
 			code++;
 			goto array;
 		default: