In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: Jason Wang <jasowang@xxxxxxxxxx> Cc: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> Cc: virtualization@xxxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- drivers/virtio/virtio_pci_modern_dev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c index 0d3dbfaf4b23..710d3bd45b4f 100644 --- a/drivers/virtio/virtio_pci_modern_dev.c +++ b/drivers/virtio/virtio_pci_modern_dev.c @@ -59,7 +59,7 @@ vp_modern_map_capability(struct virtio_pci_modern_device *mdev, int off, length -= start; - if (start + offset < offset) { + if (add_would_overflow(offset, start)) { dev_err(&dev->dev, "virtio_pci: map wrap-around %u+%u\n", start, offset); @@ -81,7 +81,7 @@ vp_modern_map_capability(struct virtio_pci_modern_device *mdev, int off, if (len) *len = length; - if (minlen + offset < minlen || + if (add_would_overflow(minlen, offset) || minlen + offset > pci_resource_len(dev, bar)) { dev_err(&dev->dev, "virtio_pci: map virtio %zu@%u " -- 2.34.1
