Commit 3f63a1d7 authored by Keir Fraser's avatar Keir Fraser Committed by Michael S. Tsirkin
Browse files

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: default avatarKeir Fraser <keirf@google.com>
Link: https://lore.kernel.org/r/20220323140727.3499235-1-keirf@google.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent eb4cecb4

drivers/virtio/virtio_pci_modern.c

+9 −3
Original line number Diff line number Diff line
@@ -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;

drivers/virtio/virtio_pci_modern_dev.c

+8 −1
Original line number Diff line number Diff line
@@ -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) {