Re: [PATCH] iio: backend: fix uninitialized data in debugfs

[Maxwell Doose]

On Mon, May 25, 2026 at 2:17 AM Dan Carpenter <error27@xxxxxxxxx> wrote:
>
> If the *ppos value is non-zero then simple_write_to_buffer() will not
> initialize the start of the buf[] buffer.  Non-zero ppos values aren't
> going to work at all.  Check for that at the start of the function and
> return -EINVAL.
>

Commit message is incorrect, it looks like you're returning -ENOSPC here...

>
> Fixes: cdf01e0809a4 ("iio: backend: add debugFs interface")
> Signed-off-by: Dan Carpenter <error27@xxxxxxxxx>
> ---
>  drivers/iio/industrialio-backend.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index 138ebebc9c0d..4763e224ebc6 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -156,7 +156,7 @@ static ssize_t iio_backend_debugfs_write_reg(struct file *file,
>         ssize_t rc;
>         int ret;
>
> -       if (count >= sizeof(buf))
> +       if (*ppos != 0 || count >= sizeof(buf))
>                 return -ENOSPC;
>

See above comment.

best regards,
max


>
>         rc = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, count);
> --
> 2.53.0
>
>