linux-kernel - [PATCH] i2c: Fix OOB access in trace_event_raw_event_smbus

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Message-ID: <20250821012312.3591166-1-zhangxiaomeng13@huawei.com>
Date: Thu, 21 Aug 2025 01:23:12 +0000
From: Xiaomeng Zhang <zhangxiaomeng13@...wei.com>
To: <rostedt@...dmis.org>, <mhiramat@...nel.org>, <dhowells@...hat.com>,
	<wsa@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <linux-trace-kernel@...r.kernel.org>
Subject: [PATCH] i2c: Fix OOB access in trace_event_raw_event_smbus_write

The smbus_write tracepoint copies __entry->len bytes into a fixed
I2C_SMBUS_BLOCK_MAX + 2 buffer. Oversized lengths (e.g., 46)
exceed the destination and over-read the source buffer, triggering
OOB warning:

memcpy: detected field-spanning write (size 48) of single field
"entry->buf" at include/trace/events/smbus.h:60 (size 34)

Clamp the copy size to I2C_SMBUS_BLOCK_MAX + 2 before memcpy().
This only affects tracing and does not change I2C transfer behavior.

Fixes: 8a325997d95d ("i2c: Add message transfer tracepoints for SMBUS [ver #2]")
Signed-off-by: Xiaomeng Zhang <zhangxiaomeng13@...wei.com>
---
 include/trace/events/smbus.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/trace/events/smbus.h b/include/trace/events/smbus.h
index 71a87edfc46d..e306d8b928c3 100644
--- a/include/trace/events/smbus.h
+++ b/include/trace/events/smbus.h
@@ -57,6 +57,8 @@ TRACE_EVENT_CONDITION(smbus_write,
 		case I2C_SMBUS_I2C_BLOCK_DATA:
 			__entry->len = data->block[0] + 1;
 		copy:
+			if (__entry->len > I2C_SMBUS_BLOCK_MAX + 2)
+				__entry->len = I2C_SMBUS_BLOCK_MAX + 2;
 			memcpy(__entry->buf, data->block, __entry->len);
 			break;
 		case I2C_SMBUS_QUICK:
-- 
2.34.1