On Mon, Jan 22, 2024 at 04:27:45PM -0800, Kees Cook 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: Bjorn Andersson <anders...@kernel.org>
Acked-by: Bjorn Andersson <anders...@kernel.org>
Regards,
Bjorn
> Cc: Mathieu Poirier <mathieu.poir...@linaro.org>
> Cc: linux-remotep...@vger.kernel.org
> Signed-off-by: Kees Cook <keesc...@chromium.org>
> ---
> drivers/remoteproc/pru_rproc.c | 2 +-
> drivers/remoteproc/remoteproc_elf_loader.c | 2 +-
> drivers/remoteproc/remoteproc_virtio.c | 4 ++--
> 3 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
> index 327f0c7ee3d6..834249ee3dd3 100644
> --- a/drivers/remoteproc/pru_rproc.c
> +++ b/drivers/remoteproc/pru_rproc.c
> @@ -893,7 +893,7 @@ pru_rproc_find_interrupt_map(struct device *dev, const
> struct firmware *fw)
> continue;
>
> /* make sure we have the entire irq map */
> - if (offset + size > fw->size || offset + size < size) {
> + if (offset + size > fw->size || add_would_overflow(size,
> offset)) {
> dev_err(dev, ".pru_irq_map section truncated\n");
> return ERR_PTR(-EINVAL);
> }
> diff --git a/drivers/remoteproc/remoteproc_elf_loader.c
> b/drivers/remoteproc/remoteproc_elf_loader.c
> index 94177e416047..b9231cf46d68 100644
> --- a/drivers/remoteproc/remoteproc_elf_loader.c
> +++ b/drivers/remoteproc/remoteproc_elf_loader.c
> @@ -278,7 +278,7 @@ find_table(struct device *dev, const struct firmware *fw)
> table = (struct resource_table *)(elf_data + offset);
>
> /* make sure we have the entire table */
> - if (offset + size > fw_size || offset + size < size) {
> + if (offset + size > fw_size || add_would_overflow(size,
> offset)) {
> dev_err(dev, "resource table truncated\n");
> return NULL;
> }
> diff --git a/drivers/remoteproc/remoteproc_virtio.c
> b/drivers/remoteproc/remoteproc_virtio.c
> index 83d76915a6ad..58742c666e35 100644
> --- a/drivers/remoteproc/remoteproc_virtio.c
> +++ b/drivers/remoteproc/remoteproc_virtio.c
> @@ -298,7 +298,7 @@ static void rproc_virtio_get(struct virtio_device *vdev,
> unsigned int offset,
> rsc = (void *)rvdev->rproc->table_ptr + rvdev->rsc_offset;
> cfg = &rsc->vring[rsc->num_of_vrings];
>
> - if (offset + len > rsc->config_len || offset + len < len) {
> + if (offset + len > rsc->config_len || add_would_overflow(len, offset)) {
> dev_err(&vdev->dev, "rproc_virtio_get: access out of bounds\n");
> return;
> }
> @@ -316,7 +316,7 @@ static void rproc_virtio_set(struct virtio_device *vdev,
> unsigned int offset,
> rsc = (void *)rvdev->rproc->table_ptr + rvdev->rsc_offset;
> cfg = &rsc->vring[rsc->num_of_vrings];
>
> - if (offset + len > rsc->config_len || offset + len < len) {
> + if (offset + len > rsc->config_len || add_would_overflow(len, offset)) {
> dev_err(&vdev->dev, "rproc_virtio_set: access out of bounds\n");
> return;
> }
> --
> 2.34.1
>
