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Date:   Tue, 22 Mar 2022 09:20:27 +0000
From:   Keir Fraser <keirf@google.com>
To:     Jason Wang <jasowang@redhat.com>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        virtualization <virtualization@lists.linux-foundation.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] virtio: pci: Sanity check the bar index in find_shm_cap
Message-ID: <YjmU22PnTLEy58+V@google.com>
References: <20220321154931.859511-1-keirf@google.com>
 <CACGkMEuEh+vsDok6hrp96kgGHkxbmzskFMJOouR3mo3d3VjwdQ@mail.gmail.com>
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On Tue, Mar 22, 2022 at 11:36:23AM +0800, Jason Wang wrote:
> On Mon, Mar 21, 2022 at 11:49 PM Keir Fraser <keirf@google.com> wrote:
> >
> > The bar index is used as an index into the device's resource list
> > and should be checked as within range for a standard bar.
> >
> > Signed-off-by: Keir Fraser <keirf@google.com>
> 
> Patch looks good, do we need a similar check in vp_modern_map_capability()?

Yes it looks like we do. Would you like me to fix that also? If so: separate patch, or
revised version of this patch?

> Thanks
> 
> > ---
> >  drivers/virtio/virtio_pci_modern.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index 5455bc041fb6..84bace98dff5 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -293,7 +293,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
> >
> >         for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR); pos > 0;
> >              pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
> > -               u8 type, cap_len, id;
> > +               u8 type, cap_len, id, res_bar;
> >                 u32 tmp32;
> >                 u64 res_offset, res_length;
> >
> > @@ -317,7 +317,12 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
> >
> >                 /* Type, and ID match, looks good */
> >                 pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
> > -                                                        bar), bar);
> > +                                                        bar), &res_bar);
> > +               if (res_bar >= PCI_STD_NUM_BARS) {
> > +                       dev_err(&dev->dev, "%s: shm cap with bad bar: %d\n",
> > +                               __func__, res_bar);
> > +                       continue;
> > +               }
> >
> >                 /* Read the lower 32bit of length and offset */
> >                 pci_read_config_dword(dev, pos + offsetof(struct virtio_pci_cap,
> > @@ -337,6 +342,7 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
> >                                                      length_hi), &tmp32);
> >                 res_length |= ((u64)tmp32) << 32;
> >
> > +               *bar = res_bar;
> >                 *offset = res_offset;
> >                 *len = res_length;
> >
> > --
> > 2.35.1.894.gb6a874cedc-goog
> >
>