linux-kernel - [PATCH] virtio: pci: Sanity check the bar index in find_shm

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Message-Id: <20220321154931.859511-1-keirf@google.com>
Date:   Mon, 21 Mar 2022 15:49:31 +0000
From:   Keir Fraser <keirf@...gle.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
Cc:     Keir Fraser <keirf@...gle.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] virtio: pci: Sanity check the bar index in find_shm_cap

The bar index is used as an index into the device's resource list
and should be checked as within range for a standard bar.

Signed-off-by: Keir Fraser <keirf@...gle.com>
---
 drivers/virtio/virtio_pci_modern.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 5455bc041fb6..84bace98dff5 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;
 
@@ -317,7 +317,12 @@ static int virtio_pci_find_shm_cap(struct pci_dev *dev, u8 required_id,
 
 		/* 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) {
+			dev_err(&dev->dev, "%s: shm cap with bad bar: %d\n",
+				__func__, res_bar);
+			continue;
+		}
 
 		/* 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;
 
-- 
2.35.1.894.gb6a874cedc-goog