linux-kernel - Re: [PATCH] ACPI: scan: Fix DMA range assignment

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Date:   Wed, 19 Oct 2022 10:13:23 +0200
From:   Lorenzo Pieralisi <lpieralisi@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     rafael@...nel.org, lvjianmin@...ngson.cn, yangyicong@...wei.com,
        chenhuacai@...ngson.cn, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, lenb@...nel.org,
        jeremy.linton@....com
Subject: Re: [PATCH] ACPI: scan: Fix DMA range assignment

On Tue, Oct 18, 2022 at 02:14:04PM +0100, Robin Murphy wrote:
> Assigning the device's dma_range_map from the iterator variable after
> the loop means it always points to the empty terminator at the end of
> the map, which is not what we want. Similarly, freeing the iterator on
> error when it points to somwhere in the middle of the allocated array
> won't work either. Fix this.
> 
> Fixes: bf2ee8d0c385 ("ACPI: scan: Support multiple DMA windows with different offsets")
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>  drivers/acpi/scan.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

A quick comment below, otherwise:

Reviewed-by: Lorenzo Pieralisi <lpieralisi@...nel.org>

> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 558664d169fc..024cc373a197 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1509,9 +1509,12 @@ int acpi_dma_get_range(struct device *dev, const struct bus_dma_region **map)
>  			goto out;
>  		}
>  
> +		*map = r;

I wonder whether having a local variable to stash the base pointer
would make code easier to read (so that we avoid using *map for that
purpose and also to return the array to the caller).

Thanks for fixing it so promptly.

Lorenzo

> +
>  		list_for_each_entry(rentry, &list, node) {
>  			if (rentry->res->start >= rentry->res->end) {
> -				kfree(r);
> +				kfree(*map);
> +				*map = NULL;
>  				ret = -EINVAL;
>  				dev_dbg(dma_dev, "Invalid DMA regions configuration\n");
>  				goto out;
> @@ -1523,8 +1526,6 @@ int acpi_dma_get_range(struct device *dev, const struct bus_dma_region **map)
>  			r->offset = rentry->offset;
>  			r++;
>  		}
> -
> -		*map = r;
>  	}
>   out:
>  	acpi_dev_free_resource_list(&list);
> -- 
> 2.36.1.dirty
>