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

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Message-ID: <CAJZ5v0huuJj_B_zeOyx4NxA6chyvebCBLvrQx8+O=++_=oOQdQ@mail.gmail.com>
Date:   Wed, 19 Oct 2022 20:30:27 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Lorenzo Pieralisi <lpieralisi@...nel.org>,
        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 Wed, Oct 19, 2022 at 10:13 AM Lorenzo Pieralisi
<lpieralisi@...nel.org> wrote:
>
> 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>

Applied as is and the code may be cleaned up later.

Thanks!

> > 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
> >