linux-kernel - Re: [PATCH] virtio: pci: Sanity check the bar index in find_shm

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Message-ID: <20220322092255-mutt-send-email-mst@kernel.org>
Date:   Tue, 22 Mar 2022 09:23:21 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Keir Fraser <keirf@...gle.com>
Cc:     Jason Wang <jasowang@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virtio: pci: Sanity check the bar index in find_shm_cap

On Tue, Mar 22, 2022 at 09:20:27AM +0000, Keir Fraser wrote:
> 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@...gle.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@...gle.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?

Yes pls. A fixed version is better, less work for everyone.

> > 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
> > >
> >