linux-kernel - Re: [PATCH] PCI: Check value of resource alignment before using _

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Message-ID: <YIEa/5E45SzKzvuf@unreal>
Date:   Thu, 22 Apr 2021 09:43:11 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Amey Narkhede <ameynarkhede03@...il.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: Check value of resource alignment before using __ffs

On Thu, Apr 22, 2021 at 12:17:47AM +0530, Amey Narkhede wrote:
> Return value of __ffs is undefined if no set bit exists in
> its argument. This indicates that the associated BAR has
> invalid alignment.
> 
> Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
> ---
>  drivers/pci/setup-bus.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index 2ce636937c6e..44e8449418ae 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1044,6 +1044,11 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
>  			 * resources.
>  			 */
>  			align = pci_resource_alignment(dev, r);
> +			if (!align) {
> +				pci_warn(dev, "BAR %d: %pR has bogus alignment\n",
> +					 i, r);
> +				continue;
> +			}

I see that you copied it from pdev_sort_resources(), but it is
incorrect change, see how negative order is handled and later
ARRAY_SIZE() check.

Thanks

>  			order = __ffs(align) - 20;
>  			if (order < 0)
>  				order = 0;
> --
> 2.31.1