On Wed, Mar 23, 2022 at 10:07 PM Keir Fraser <keirf@xxxxxxxxxx> 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@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> ---
> 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
>
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