linux-kernel - [PATCH 3.2 30/92] drm/vmwgfx: Make sure user-space can't DMA across buffer object boundaries v2

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Date:	Sat, 07 Jun 2014 02:26:28 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Thomas Hellstrom" <thellstrom@...are.com>,
	"Jakob Bornecrantz" <jakob@...are.com>
Subject: [PATCH 3.2 30/92] drm/vmwgfx: Make sure user-space can't DMA
 across buffer object boundaries v2

3.2.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Hellstrom <thellstrom@...are.com>

commit cbd75e97a525e3819c02dc18bc2d67aa544c9e45 upstream.

We already check that the buffer object we're accessing is registered with
the file. Now also make sure that we can't DMA across buffer object boundaries.

v2: Code commenting update.

Signed-off-by: Thomas Hellstrom <thellstrom@...are.com>
Reviewed-by: Jakob Bornecrantz <jakob@...are.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -558,14 +558,36 @@ static int vmw_cmd_dma(struct vmw_privat
 	} *cmd;
 	int ret;
 	struct vmw_resource *res;
+	SVGA3dCmdSurfaceDMASuffix *suffix;
+	uint32_t bo_size;
 
 	cmd = container_of(header, struct vmw_dma_cmd, header);
+	suffix = (SVGA3dCmdSurfaceDMASuffix *)((unsigned long) &cmd->dma +
+					       header->size - sizeof(*suffix));
+
+	/* Make sure device and verifier stays in sync. */
+	if (unlikely(suffix->suffixSize != sizeof(*suffix))) {
+		DRM_ERROR("Invalid DMA suffix size.\n");
+		return -EINVAL;
+	}
+
 	ret = vmw_translate_guest_ptr(dev_priv, sw_context,
 				      &cmd->dma.guest.ptr,
 				      &vmw_bo);
 	if (unlikely(ret != 0))
 		return ret;
 
+	/* Make sure DMA doesn't cross BO boundaries. */
+	bo_size = vmw_bo->base.num_pages * PAGE_SIZE;
+	if (unlikely(cmd->dma.guest.ptr.offset > bo_size)) {
+		DRM_ERROR("Invalid DMA offset.\n");
+		return -EINVAL;
+	}
+
+	bo_size -= cmd->dma.guest.ptr.offset;
+	if (unlikely(suffix->maximumOffset > bo_size))
+		suffix->maximumOffset = bo_size;
+
 	bo = &vmw_bo->base;
 	ret = vmw_user_surface_lookup_handle(dev_priv, sw_context->tfile,
 					     cmd->dma.host.sid, &srf);

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