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From:   Oleksandr Andrushchenko <andr2000@gmail.com>
To:     xen-devel@lists.xenproject.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, boris.ostrovsky@oracle.com,
        jgross@suse.com, airlied@linux.ie, daniel@ffwll.ch
Cc:     sstabellini@kernel.org, dan.carpenter@oracle.com,
        intel-gfx@lists.freedesktop.org,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
        stable@vger.kernel.org
Subject: [PATCH v2 1/5] xen/gntdev: Fix dmabuf import with non-zero sgt offset
Date:   Thu, 13 Aug 2020 09:21:09 +0300
Message-Id: <20200813062113.11030-2-andr2000@gmail.com>
In-Reply-To: <20200813062113.11030-1-andr2000@gmail.com>
References: <20200813062113.11030-1-andr2000@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

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>
---
 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 75d3bb948bf3..b1b6eebafd5d 100644
--- a/drivers/xen/gntdev-dmabuf.c
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -613,6 +613,14 @@ 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);
-- 
2.17.1