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 <[email protected]> 发送时间: 2025年9月3日 3:50 收件人: zhangxiaomeng (A) <[email protected]> 抄送: [email protected]; [email protected]; [email protected]; [email protected]; [email protected] 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 <[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
