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SubjectRe: [PATCH] i2c: core-smbus: don't trace smbus_reply data on errors
On Thu, Jan 03, 2019 at 09:49:27PM -0500, Steven Rostedt wrote:
> On Thu, 3 Jan 2019 16:42:03 -0800
> John Sperbeck <jsperbeck@google.com> wrote:
>
> > If an smbus transfer fails, there's no guarantee that the output
> > buffer was written. So, avoid copying from 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.
> >
> > Signed-off-by: John Sperbeck <jsperbeck@google.com>
> > ---
> > drivers/i2c/i2c-core-smbus.c | 2 +-
> > include/trace/events/smbus.h | 10 +++++-----
> > 2 files changed, 6 insertions(+), 6 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..b6376a7c7e74 100644
> > --- a/include/trace/events/smbus.h
> > +++ b/include/trace/events/smbus.h
> > @@ -138,8 +138,8 @@ 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),
> > + const union i2c_smbus_data *data, int res),
> > + TP_ARGS(adap, addr, flags, read_write, command, protocol, data, res),
> > TP_CONDITION(read_write == I2C_SMBUS_READ),
>
> Hmm, instead of tracing nothing, as this is already a "conditional
> trace event", why not add to that condition:
>
> TP_CONDITION(res >= 0 && read_write == I2C_SMBUS_READ),
>
> Unless you want to still trace some data on failure.

John, any comment to this?

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