Re: [PATCH v3] virtio: pci: check bar values read from virtio config space
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From: Jason Wang <hidden>
Date: 2022-03-30 02:44:02
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On Wed, Mar 23, 2022 at 10:07 PM Keir Fraser [off-list ref] 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 <redacted>
Acked-by: Jason Wang <redacted>
quoted hunk
--- 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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