| Message ID | 20240123002814.1396804-77-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
On Tue, Jan 23, 2024 at 2:28 AM Kees Cook <keescook@chromium.org> wrote: > > 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@redhat.com> > Cc: Jason Wang <jasowang@redhat.com> > Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > Cc: virtualization@lists.linux.dev > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Eugenio Pérez <eperezma@redhat.com> > --- > 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 > >
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 "
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@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com> Cc: virtualization@lists.linux.dev Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/virtio/virtio_pci_modern_dev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)