From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> commit 5fa4e6f1c2d8c9a4e47e1931b42893172d388f2b upstream. It is possible that the scatter-gather table during dmabuf import has non-zero offset of the data, but user-space doesn't expect that. Fix this by failing the import, so user-space doesn't access wrong data. Fixes: bf8dc55b1358 ("xen/gntdev: Implement dma-buf import functionality") Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> Acked-by: Juergen Gross <jgross@suse.com> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20200813062113.11030-2-andr2000@gmail.com Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- drivers/xen/gntdev-dmabuf.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c index d97fcfc5e5587..f6589563ff711 100644 --- a/drivers/xen/gntdev-dmabuf.c +++ b/drivers/xen/gntdev-dmabuf.c @@ -641,6 +641,14 @@ dmabuf_imp_to_refs(struct gntdev_dmabuf_priv *priv, struct device *dev, goto fail_detach; } + /* Check that we have zero offset. */ + if (sgt->sgl->offset) { + ret = ERR_PTR(-EINVAL); + pr_debug("DMA buffer has %d bytes offset, user-space expects 0\n", + sgt->sgl->offset); + goto fail_unmap; + } + /* Check number of pages that imported buffer has. */ if (attach->dmabuf->size != gntdev_dmabuf->nr_pages << PAGE_SHIFT) { ret = ERR_PTR(-EINVAL); -- 2.25.1