2022-03-25 19:15:45

by Keir Fraser

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

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 <[email protected]>
---
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

2022-03-30 02:00:12

by Keir Fraser

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

Ping.

If you prefer I could read the capability offset and length in
virtio_pci_find_capability() and communicate them to
vp_modern_map_capability(), perhaps via a new struct virtio_pci_cap
used for only this purpose?


On Wed, Mar 23, 2022 at 02:07:27PM +0000, Keir Fraser 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 <[email protected]>
> ---
> 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
>

2022-03-30 11:50:35

by Jason Wang

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

On Wed, Mar 23, 2022 at 10:07 PM Keir Fraser <[email protected]> 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 <[email protected]>

Acked-by: Jason Wang <[email protected]>

> ---
> 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
>

2022-03-31 03:43:00

by Michael S. Tsirkin

Subject: Re: [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 <[email protected]> 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 <[email protected]>
>
> Acked-by: Jason Wang <[email protected]>
>


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
> >