回复: [PATCH] i2c: Fix OOB access in trace_event_raw_event_smbus_write
From: zhangxiaomeng (A) <hidden>
Date: 2025-09-09 09:30:11
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I previously attempted to apply a fix within the i2cdev_ioctl_smbus function. While this approach was successful in preventing the warning, I found that the required changes were quite extensive. The WARN is triggered by the trace_smbus_write tracepoint, which performs a memcpy(__entry->buf, data->block, len) for write operations on three specific block protocols: I2C_SMBUS_BLOCK_DATA, I2C_SMBUS_I2C_BLOCK_DATA, and I2C_SMBUS_BLOCK_PROC_CALL. To fix this in i2cdev_ioctl_smbus, it would be necessary to add checks for all three of these cases, which makes the solution rather complex. --xiaomeng -----邮件原件----- 发件人: Steven Rostedt [off-list ref] 发送时间: 2025年9月3日 3:50 收件人: zhangxiaomeng (A) [off-list ref] 抄送: mhiramat@kernel.org; dhowells@redhat.com; wsa@kernel.org; linux-kernel@vger.kernel.org; linux-trace-kernel@vger.kernel.org 主题: Re: [PATCH] i2c: Fix OOB access in trace_event_raw_event_smbus_write On Thu, 21 Aug 2025 01:23:12 +0000 Xiaomeng Zhang [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- include/trace/events/smbus.h | 2 ++ 1 file changed, 2 insertions(+)diff --git a/include/trace/events/smbus.hb/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:
The code has:
switch (protocol) {
case I2C_SMBUS_BYTE_DATA:
__entry->len = 1;
goto copy;
case I2C_SMBUS_WORD_DATA:
case I2C_SMBUS_PROC_CALL:
__entry->len = 2;
goto copy;
case I2C_SMBUS_BLOCK_DATA:
case I2C_SMBUS_BLOCK_PROC_CALL:
case I2C_SMBUS_I2C_BLOCK_DATA:
__entry->len = data->block[0] + 1;
copy:
memcpy(__entry->buf, data->block, __entry->len);
break;
case I2C_SMBUS_QUICK:
case I2C_SMBUS_BYTE:
case I2C_SMBUS_I2C_BLOCK_BROKEN:
default:
__entry->len = 0;
}
I only see two calls to the copy where one is len = 1 and the other is len = 2. Why not put the check before the copy label?
-- Steve