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SubjectRe: [PATCH v2] i2c: core-smbus: don't trace smbus_reply data on errors
On Sun, 10 Feb 2019 19:40:21 -0800
John Sperbeck <jsperbeck@google.com> wrote:

> If an smbus transfer fails, there's no guarantee that the output
> buffer was written. So, avoid trying to show the output buffer when
> tracing after an error. This was 'mostly harmless', but would trip
> up kasan checking if left-over cruft in byte 0 is a large length,
> causing us to read from unwritten memory.

This looks fine to me, but I'm not sure how the i2c maintainers feel,
but I always require that a new patch version starts a new thread, and
not be part of a older thread release (causes these patches to be
hidden from those that read patches in threading mode).

-- Steve

>
> Signed-off-by: John Sperbeck <jsperbeck@google.com>
> ---
> drivers/i2c/i2c-core-smbus.c | 2 +-
> include/trace/events/smbus.h | 6 +++---
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> index 9cd66cabb84f..132119112596 100644
> --- a/drivers/i2c/i2c-core-smbus.c
> +++ b/drivers/i2c/i2c-core-smbus.c
> @@ -585,7 +585,7 @@ s32 __i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
> trace:
> /* If enabled, the reply tracepoint is conditional on read_write. */
> trace_smbus_reply(adapter, addr, flags, read_write,
> - command, protocol, data);
> + command, protocol, data, res);
> trace_smbus_result(adapter, addr, flags, read_write,
> command, protocol, res);
>
> diff --git a/include/trace/events/smbus.h b/include/trace/events/smbus.h
> index d2fb6e1d3e10..a4892a187842 100644
> --- a/include/trace/events/smbus.h
> +++ b/include/trace/events/smbus.h
> @@ -138,9 +138,9 @@ TRACE_EVENT_CONDITION(smbus_reply,
> TP_PROTO(const struct i2c_adapter *adap,
> u16 addr, unsigned short flags,
> char read_write, u8 command, int protocol,
> - const union i2c_smbus_data *data),
> - TP_ARGS(adap, addr, flags, read_write, command, protocol, data),
> - TP_CONDITION(read_write == I2C_SMBUS_READ),
> + const union i2c_smbus_data *data, int res),
> + TP_ARGS(adap, addr, flags, read_write, command, protocol, data, res),
> + TP_CONDITION(res >= 0 && read_write == I2C_SMBUS_READ),
> TP_STRUCT__entry(
> __field(int, adapter_nr )
> __field(__u16, addr )

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