Re: [PATCH] iio: gyro: itg3200: fix i2c read into the wrong stack location

[Jonathan Cameron]

On Wed, 6 May 2026 08:08:24 +0100
David CARLIER <devnexen@xxxxxxxxx> wrote:

> On Wed, 6 May 2026 at 07:40, Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxx> wrote:
> >
> > On Tue, May 05, 2026 at 02:37:48PM +0100, David Carlier wrote:  
> > > itg3200_read_all_channels() takes `__be16 *buf' as a parameter and
> > > fills the i2c_msg destination as `(char *)&buf'. Since `buf' is the
> > > parameter (a pointer), `&buf' is the address of the local pointer
> > > slot on the stack of itg3200_read_all_channels(), not the address
> > > of the caller's scan buffer. The (char *) cast hides the type
> > > mismatch.
> > >
> > > i2c_transfer() therefore writes ITG3200_SCAN_ELEMENTS * sizeof(s16)
> > > = 8 bytes into the parameter's stack slot, which is discarded when
> > > the function returns. The caller's scan buffer in
> > > itg3200_trigger_handler() is never written to, so
> > > iio_push_to_buffers_with_timestamp() pushes uninitialised stack
> > > contents to userspace via /dev/iio:deviceX every scan -- both a
> > > functional bug (no actual gyroscope or temperature data is
> > > delivered through the triggered buffer) and an information leak.
> > >
> > > The non-buffered read_raw() path is unaffected: it goes through
> > > itg3200_read_reg_s16() which uses `&out' on a local s16 value,
> > > where that is correct.
> > >
> > > Drop the spurious `&' so the i2c read writes into the caller's
> > > buffer.  
> >
> > Very good catch! I'm puzzled if that code was ever tested. Do you have an HW
> > and that's how you enter to this bug?
> >
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxx>
> >
> > --
> > With Best Regards,
> > Andy Shevchenko
> >
> >  
> 
> Thanks! No HW on my side -- found by inspection. I had recently looked
>   at a similar `(char *)&buf' / `(char *)buf' mix-up in another
> driver,
>   so I went grepping for the same shape and itg3200 stood out. For
>   contrast, drivers/iio/humidity/hdc3020.c::hdc3020_read_bytes() has
> the
>   same signature (u8 *buf parameter) and assigns `.buf = buf'
> correctly.
> 
>   Compile-tested only; the analysis in the changelog is what I'm
> relying
>   on.
> 
> Cheers !

I was assuming the fixes tag was wrong and this was a result of
rework, but you are correct it goes all they way back!
Huh.  I guess last minute driver changes that didn't quite get
tested and clearly not a heavily used device!  13 years of
not working.

We could drop the driver, but it's possible it is in use
just not with buffered support (which is a separate CONFIG option)
Also drops don't get backported so we'd be leaving it broken and
stale.  So let's fix it now and consider a drop later.

Applied to the fixes-togreg branch of iio.git

Thanks,
Jonathan