Re: [PATCH] spi: bcm-qspi: return error if neither hif_mspi nor mspi is available

[Kamal Dasu]

On Thu, Jun 29, 2023 at 9:43 AM Jonas Gorski <jonas.gorski@xxxxxxxxx> wrote:
>
> If neither a "hif_mspi" nor "mspi" resource is present, the driver will
> just early exit in probe but still return success. Apart from not doing
> anything meaningful, this would then also lead to a null pointer access
> on removal, as platform_get_drvdata() would return NULL, which it would
> then try to dereferce when trying to unregister the spi master.
>
> Fix this by unconditionally calling devm_ioremap_resource(), as it can
> handle a NULL res and will then return a viable ERR_PTR() if we get one.
>
> The "return 0;" was previously a "goto qspi_resource_err;" where then
> ret was returned, but since ret was still initialized to 0 at this place
> this was a valid conversion in 63c5395bb7a9 ("spi: bcm-qspi: Fix
> use-after-free on unbind"). The issue was not introduced by this commit,
> only made more obvious.
>
> Fixes: fa236a7ef240 ("spi: bcm-qspi: Add Broadcom MSPI driver")
> Signed-off-by: Jonas Gorski <jonas.gorski@xxxxxxxxx>
> ---
> Found by looking a the driver while comparing it to its bindings.
>
> Only build tested, not runtested.
>
>  drivers/spi/spi-bcm-qspi.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c
> index 6b46a3b67c41..d91dfbe47aa5 100644
> --- a/drivers/spi/spi-bcm-qspi.c
> +++ b/drivers/spi/spi-bcm-qspi.c
> @@ -1543,13 +1543,9 @@ int bcm_qspi_probe(struct platform_device *pdev,
>                 res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
>                                                    "mspi");
>
> -       if (res) {
> -               qspi->base[MSPI]  = devm_ioremap_resource(dev, res);
> -               if (IS_ERR(qspi->base[MSPI]))
> -                       return PTR_ERR(qspi->base[MSPI]);
> -       } else {
> -               return 0;
> -       }

I would rather just do this in the else case

} else {
 -              return 0;
 +             return -ENODEV;
}

 The change below does not check the return of
platform_get_resource_byname() in my opinion rather relies on
devm_ioremap_resource() doing the right thing.

> +       qspi->base[MSPI]  = devm_ioremap_resource(dev, res);
> +       if (IS_ERR(qspi->base[MSPI]))
> +               return PTR_ERR(qspi->base[MSPI]);
>
>         res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "bspi");
>         if (res) {
> --
> 2.34.1
>

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature