Re: [PATCH] ACPI: scan: Fix DMA range assignment

From: Lorenzo Pieralisi <lpieralisi@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: rafael@kernel.org, lvjianmin@loongson.cn, yangyicong@huawei.com,
	chenhuacai@loongson.cn, linux-acpi@vger.kernel.org,
	linux-kernel@vger.kernel.org, lenb@kernel.org,
	jeremy.linton@arm.com
Subject: Re: [PATCH] ACPI: scan: Fix DMA range assignment
Date: Wed, 19 Oct 2022 10:13:23 +0200	[thread overview]
Message-ID: <Y0+xo2DO+M1iJc77@lpieralisi> (raw)
In-Reply-To: <e94f99cfe09a64c590f009d21c566339117394e2.1666098844.git.robin.murphy@arm.com>

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@arm.com>
> ---
>  drivers/acpi/scan.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

A quick comment below, otherwise:

Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.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
> 