On Thu, 21 Aug 2025 01:23:12 +0000
Xiaomeng Zhang <[email protected]> wrote:
> 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 <[email protected]>
> ---
> 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:
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
