linux-kernel - Re: [PATCH] iio: dummy: iio_simple_dummy: check the return value of kstrdup()

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Message-ID: <20211216163019.570d6aed@jic23-huawei>
Date:   Thu, 16 Dec 2021 16:30:37 +0000
From:   Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:     Xiaoke Wang <xkernel.wang@...mail.com>
Cc:     lars@...afoo.de, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: dummy: iio_simple_dummy: check the return value of
 kstrdup()

On Mon, 13 Dec 2021 17:18:21 +0800
Xiaoke Wang <xkernel.wang@...mail.com> wrote:

> kstrdup() is also a memory allocation-related function, it return NULL
> when some memory errors happen. So it is better to check the return
> value of it so to catch the memory error in time.
> 
> Signed-off-by: Xiaoke Wang <xkernel.wang@...mail.com>
Hi.

Good spot, but there is more to do to fix this.  The error path doesn't
clear up the allocation if we get a failure later in this function.

So should have a kfree() error case.

Also, a side note is the error labels in that function are terrible!
(given I probably wrote them I can be rude about them:) 

So cleaning that up as well might be a good thing to do whilst here.
Make them reflect what they are cleaning up rather that the crazy
naming there currently.  When error_ret label goes to a place where
it does more than just return it's not good.

Also drop the first error_kzalloc label and goto in favour of direct return.

Great if you can tidy this up, if not I'll do it at somepoint.

Jonathan

> ---
>  drivers/iio/dummy/iio_simple_dummy.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/iio/dummy/iio_simple_dummy.c b/drivers/iio/dummy/iio_simple_dummy.c
> index c0b7ef9..a5e8071 100644
> --- a/drivers/iio/dummy/iio_simple_dummy.c
> +++ b/drivers/iio/dummy/iio_simple_dummy.c
> @@ -616,6 +616,10 @@ static struct iio_sw_device *iio_dummy_probe(const char *name)
>  	 *    indio_dev->name = spi_get_device_id(spi)->name;
>  	 */
>  	indio_dev->name = kstrdup(name, GFP_KERNEL);
> +	if (!indio_dev->name) {
> +		ret = -ENOMEM;
> +		goto error_free_device;
> +	}
>  
>  	/* Provide description of available channels */
>  	indio_dev->channels = iio_dummy_channels;