thr3ads.net - Virtualization - [PATCH v3] virtio: pci: check bar values read from virtio config space [Mar 2022]

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Jason Wang

2022-Mar-30 02:43 UTC

[PATCH v3] virtio: pci: check bar values read from virtio config space

On Wed, Mar 23, 2022 at 10:07 PM Keir Fraser <keirf at google.com>
wrote:>
> virtio pci config structures may in future have non-standard bar
> values in the bar field. We should anticipate this by skipping any
> structures containing such a reserved value.
>
> The bar value should never change: check for harmful modified values
> we re-read it from the config space in vp_modern_map_capability().
>
> Also clean up an existing check to consistently use PCI_STD_NUM_BARS.
>
> Signed-off-by: Keir Fraser <keirf at google.com>
Acked-by: Jason Wang <jasowang at redhat.com>
> ---
>  drivers/virtio/virtio_pci_modern.c     | 12 +++++++++---
>  drivers/virtio/virtio_pci_modern_dev.c |  9 ++++++++-
>  2 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
> index 5455bc041fb6..6adfcd0297a7 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;
>
> @@ -315,9 +315,14 @@ static int virtio_pci_find_shm_cap(struct pci_dev
*dev, u8 required_id,
>                 if (id != required_id)
>                         continue;
>
> -               /* 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)
> +                       continue;
> +
> +               /* Type and ID match, and the BAR value isn't reserved.
> +                * Looks good.
> +                */
>
>                 /* 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;
>
> diff --git a/drivers/virtio/virtio_pci_modern_dev.c
b/drivers/virtio/virtio_pci_modern_dev.c
> index e8b3ff2b9fbc..591738ad3d56 100644
> --- a/drivers/virtio/virtio_pci_modern_dev.c
> +++ b/drivers/virtio/virtio_pci_modern_dev.c
> @@ -35,6 +35,13 @@ vp_modern_map_capability(struct virtio_pci_modern_device
*mdev, int off,
>         pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap,
length),
>                               &length);
>
> +       /* Check if the BAR may have changed since we requested the region.
*/
> +       if (bar >= PCI_STD_NUM_BARS || !(mdev->modern_bars & (1
<< bar))) {
> +               dev_err(&dev->dev,
> +                       "virtio_pci: bar unexpectedly changed to
%u\n", bar);
> +               return NULL;
> +       }
> +
>         if (length <= start) {
>                 dev_err(&dev->dev,
>                         "virtio_pci: bad capability len %u (>%u
expected)\n",
> @@ -120,7 +127,7 @@ static inline int virtio_pci_find_capability(struct
pci_dev *dev, u8 cfg_type,
>                                      &bar);
>
>                 /* Ignore structures with reserved BAR values */
> -               if (bar > 0x5)
> +               if (bar >= PCI_STD_NUM_BARS)
>                         continue;
>
>                 if (type == cfg_type) {
> --
> 2.35.1.894.gb6a874cedc-goog
>

Michael S. Tsirkin

2022-Mar-30 06:35 UTC

head link

[PATCH v3] virtio: pci: check bar values read from virtio config space

On Wed, Mar 30, 2022 at 10:43:40AM +0800, Jason Wang
wrote:> On Wed, Mar 23, 2022 at 10:07 PM Keir Fraser <keirf at google.com>
wrote:
> >
> > virtio pci config structures may in future have non-standard bar
> > values in the bar field. We should anticipate this by skipping any
> > structures containing such a reserved value.
> >
> > The bar value should never change: check for harmful modified values
> > we re-read it from the config space in vp_modern_map_capability().
> >
> > Also clean up an existing check to consistently use PCI_STD_NUM_BARS.
> >
> > Signed-off-by: Keir Fraser <keirf at google.com>
> 
> Acked-by: Jason Wang <jasowang at redhat.com>
> 

Thanks! I don't want to rebase anymore though so not adding this ack.
Sorry!
> >  drivers/virtio/virtio_pci_modern.c     | 12 +++++++++---
> >  drivers/virtio/virtio_pci_modern_dev.c |  9 ++++++++-
> >  2 files changed, 17 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
> > index 5455bc041fb6..6adfcd0297a7 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;
> >
> > @@ -315,9 +315,14 @@ static int virtio_pci_find_shm_cap(struct pci_dev
*dev, u8 required_id,
> >                 if (id != required_id)
> >                         continue;
> >
> > -               /* 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)
> > +                       continue;
> > +
> > +               /* Type and ID match, and the BAR value isn't
reserved.
> > +                * Looks good.
> > +                */
> >
> >                 /* 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;
> >
> > diff --git a/drivers/virtio/virtio_pci_modern_dev.c
b/drivers/virtio/virtio_pci_modern_dev.c
> > index e8b3ff2b9fbc..591738ad3d56 100644
> > --- a/drivers/virtio/virtio_pci_modern_dev.c
> > +++ b/drivers/virtio/virtio_pci_modern_dev.c
> > @@ -35,6 +35,13 @@ vp_modern_map_capability(struct
virtio_pci_modern_device *mdev, int off,
> >         pci_read_config_dword(dev, off + offsetof(struct
virtio_pci_cap, length),
> >                               &length);
> >
> > +       /* Check if the BAR may have changed since we requested the
region. */
> > +       if (bar >= PCI_STD_NUM_BARS || !(mdev->modern_bars &
(1 << bar))) {
> > +               dev_err(&dev->dev,
> > +                       "virtio_pci: bar unexpectedly changed to
%u\n", bar);
> > +               return NULL;
> > +       }
> > +
> >         if (length <= start) {
> >                 dev_err(&dev->dev,
> >                         "virtio_pci: bad capability len %u
(>%u expected)\n",
> > @@ -120,7 +127,7 @@ static inline int
virtio_pci_find_capability(struct pci_dev *dev, u8 cfg_type,
> >                                      &bar);
> >
> >                 /* Ignore structures with reserved BAR values */
> > -               if (bar > 0x5)
> > +               if (bar >= PCI_STD_NUM_BARS)
> >                         continue;
> >
> >                 if (type == cfg_type) {
> > --
> > 2.35.1.894.gb6a874cedc-goog
> >

Virtualization - Mar 2022 - [PATCH v3] virtio: pci: check bar values read from virtio config space

[PATCH v3] virtio: pci: check bar values read from virtio config space

[PATCH v3] virtio: pci: check bar values read from virtio config space