linux-kernel - Re: [PATCH] iio: light: isl29028: Fix the warning in isl29028

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Date:   Sat, 16 Jul 2022 19:28:50 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Zheyu Ma <zheyuma97@...il.com>
Cc:     lars@...afoo.de, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: light: isl29028: Fix the warning in
 isl29028_remove()

On Fri, 15 Jul 2022 21:29:09 +0800
Zheyu Ma <zheyuma97@...il.com> wrote:

> The driver uses managed resource API to register the iio device, so it
> is unnecessarg to unregister the device manually.
> 
> The following log reveals it:
> 
> [   32.374955] isl29028 0-0010: remove
> [   32.376861] general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN PTI
> [   32.377676] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
> [   32.379432] RIP: 0010:kernfs_find_and_get_ns+0x28/0xe0
> [   32.385461] Call Trace:
> [   32.385807]  sysfs_unmerge_group+0x59/0x110
> [   32.386110]  dpm_sysfs_remove+0x58/0xc0
> [   32.386391]  device_del+0x296/0xe50
> [   32.386959]  cdev_device_del+0x1d/0xd0
> [   32.387231]  devm_iio_device_unreg+0x27/0xb0
> [   32.387542]  devres_release_group+0x319/0x3d0
> [   32.388162]  i2c_device_remove+0x93/0x1f0
> 
> Fixes: 2db5054ac28d ("staging: iio: isl29028: add runtime power management support")
> Signed-off-by: Zheyu Ma <zheyuma97@...il.com>

Unfortunately the fix still leaves the release order as not mirroring the ordering
in probe.  As such, I think the right fix is to not use devm_iio_device_register()
but rather use the non managed form.

Thanks,

Jonathan
> ---
>  drivers/iio/light/isl29028.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/iio/light/isl29028.c b/drivers/iio/light/isl29028.c
> index 9de3262aa688..505235903bd8 100644
> --- a/drivers/iio/light/isl29028.c
> +++ b/drivers/iio/light/isl29028.c
> @@ -641,8 +641,6 @@ static int isl29028_remove(struct i2c_client *client)
>  	struct iio_dev *indio_dev = i2c_get_clientdata(client);
>  	struct isl29028_chip *chip = iio_priv(indio_dev);
>  
> -	iio_device_unregister(indio_dev);
> -
>  	pm_runtime_disable(&client->dev);
>  	pm_runtime_set_suspended(&client->dev);
>