[PATCH 4.2 106/110] drm/vmwgfx: Fix up user_dmabuf refcounting

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.2-stable review patch.  If anyone has any objections, please let me know.

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

From: Thomas Hellstrom <thellstrom@vmware.com>

commit 54c12bc374408faddbff75dbf1a6167c19af39c4 upstream.

If user space calls unreference on a user_dmabuf it will typically
kill the struct ttm_base_object member which is responsible for the
user-space visibility. However the dmabuf part may still be alive and
refcounted. In some situations, like for shared guest-backed surface
referencing/opening, the driver may try to reference the
struct ttm_base_object member again, causing an immediate kernel warning
and a later kernel NULL pointer dereference.

Fix this by always maintaining a reference on the struct
ttm_base_object member, in situations where it might subsequently be
referenced.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c      |    3 +++
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.h      |    6 ++++--
 drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c  |    6 ++++--
 drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c  |    2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_resource.c |   29 +++++++++++++++++++++--------
 drivers/gpu/drm/vmwgfx/vmwgfx_shader.c   |    2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_surface.c  |   12 +++++++++---
 7 files changed, 43 insertions(+), 17 deletions(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -1458,6 +1458,9 @@ static void __exit vmwgfx_exit(void)
 	drm_pci_exit(&driver, &vmw_pci_driver);
 }
 
+MODULE_INFO(vmw_patch, "ed7d78b2");
+MODULE_INFO(vmw_patch, "54c12bc3");
+
 module_init(vmwgfx_init);
 module_exit(vmwgfx_exit);
 
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -636,7 +636,8 @@ extern int vmw_user_dmabuf_alloc(struct
 				 uint32_t size,
 				 bool shareable,
 				 uint32_t *handle,
-				 struct vmw_dma_buffer **p_dma_buf);
+				 struct vmw_dma_buffer **p_dma_buf,
+				 struct ttm_base_object **p_base);
 extern int vmw_user_dmabuf_reference(struct ttm_object_file *tfile,
 				     struct vmw_dma_buffer *dma_buf,
 				     uint32_t *handle);
@@ -650,7 +651,8 @@ extern uint32_t vmw_dmabuf_validate_node
 					 uint32_t cur_validate_node);
 extern void vmw_dmabuf_validate_clear(struct ttm_buffer_object *bo);
 extern int vmw_user_dmabuf_lookup(struct ttm_object_file *tfile,
-				  uint32_t id, struct vmw_dma_buffer **out);
+				  uint32_t id, struct vmw_dma_buffer **out,
+				  struct ttm_base_object **base);
 extern int vmw_stream_claim_ioctl(struct drm_device *dev, void *data,
 				  struct drm_file *file_priv);
 extern int vmw_stream_unref_ioctl(struct drm_device *dev, void *data,
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -887,7 +887,8 @@ static int vmw_translate_mob_ptr(struct
 	struct vmw_relocation *reloc;
 	int ret;
 
-	ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo);
+	ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo,
+				     NULL);
 	if (unlikely(ret != 0)) {
 		DRM_ERROR("Could not find or use MOB buffer.\n");
 		ret = -EINVAL;
@@ -949,7 +950,8 @@ static int vmw_translate_guest_ptr(struc
 	struct vmw_relocation *reloc;
 	int ret;
 
-	ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo);
+	ret = vmw_user_dmabuf_lookup(sw_context->fp->tfile, handle, &vmw_bo,
+				     NULL);
 	if (unlikely(ret != 0)) {
 		DRM_ERROR("Could not find or use GMR region.\n");
 		ret = -EINVAL;
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c
@@ -484,7 +484,7 @@ int vmw_overlay_ioctl(struct drm_device
 		goto out_unlock;
 	}
 
-	ret = vmw_user_dmabuf_lookup(tfile, arg->handle, &buf);
+	ret = vmw_user_dmabuf_lookup(tfile, arg->handle, &buf, NULL);
 	if (ret)
 		goto out_unlock;
 
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
@@ -356,7 +356,7 @@ int vmw_user_lookup_handle(struct vmw_pr
 	}
 
 	*out_surf = NULL;
-	ret = vmw_user_dmabuf_lookup(tfile, handle, out_buf);
+	ret = vmw_user_dmabuf_lookup(tfile, handle, out_buf, NULL);
 	return ret;
 }
 
@@ -483,7 +483,8 @@ int vmw_user_dmabuf_alloc(struct vmw_pri
 			  uint32_t size,
 			  bool shareable,
 			  uint32_t *handle,
-			  struct vmw_dma_buffer **p_dma_buf)
+			  struct vmw_dma_buffer **p_dma_buf,
+			  struct ttm_base_object **p_base)
 {
 	struct vmw_user_dma_buffer *user_bo;
 	struct ttm_buffer_object *tmp;
@@ -517,6 +518,10 @@ int vmw_user_dmabuf_alloc(struct vmw_pri
 	}
 
 	*p_dma_buf = &user_bo->dma;
+	if (p_base) {
+		*p_base = &user_bo->prime.base;
+		kref_get(&(*p_base)->refcount);
+	}
 	*handle = user_bo->prime.base.hash.key;
 
 out_no_base_object:
@@ -633,6 +638,7 @@ int vmw_user_dmabuf_synccpu_ioctl(struct
 	struct vmw_dma_buffer *dma_buf;
 	struct vmw_user_dma_buffer *user_bo;
 	struct ttm_object_file *tfile = vmw_fpriv(file_priv)->tfile;
+	struct ttm_base_object *buffer_base;
 	int ret;
 
 	if ((arg->flags & (drm_vmw_synccpu_read | drm_vmw_synccpu_write)) == 0
@@ -645,7 +651,8 @@ int vmw_user_dmabuf_synccpu_ioctl(struct
 
 	switch (arg->op) {
 	case drm_vmw_synccpu_grab:
-		ret = vmw_user_dmabuf_lookup(tfile, arg->handle, &dma_buf);
+		ret = vmw_user_dmabuf_lookup(tfile, arg->handle, &dma_buf,
+					     &buffer_base);
 		if (unlikely(ret != 0))
 			return ret;
 
@@ -653,6 +660,7 @@ int vmw_user_dmabuf_synccpu_ioctl(struct
 				       dma);
 		ret = vmw_user_dmabuf_synccpu_grab(user_bo, tfile, arg->flags);
 		vmw_dmabuf_unreference(&dma_buf);
+		ttm_base_object_unref(&buffer_base);
 		if (unlikely(ret != 0 && ret != -ERESTARTSYS &&
 			     ret != -EBUSY)) {
 			DRM_ERROR("Failed synccpu grab on handle 0x%08x.\n",
@@ -694,7 +702,8 @@ int vmw_dmabuf_alloc_ioctl(struct drm_de
 		return ret;
 
 	ret = vmw_user_dmabuf_alloc(dev_priv, vmw_fpriv(file_priv)->tfile,
-				    req->size, false, &handle, &dma_buf);
+				    req->size, false, &handle, &dma_buf,
+				    NULL);
 	if (unlikely(ret != 0))
 		goto out_no_dmabuf;
 
@@ -723,7 +732,8 @@ int vmw_dmabuf_unref_ioctl(struct drm_de
 }
 
 int vmw_user_dmabuf_lookup(struct ttm_object_file *tfile,
-			   uint32_t handle, struct vmw_dma_buffer **out)
+			   uint32_t handle, struct vmw_dma_buffer **out,
+			   struct ttm_base_object **p_base)
 {
 	struct vmw_user_dma_buffer *vmw_user_bo;
 	struct ttm_base_object *base;
@@ -745,7 +755,10 @@ int vmw_user_dmabuf_lookup(struct ttm_ob
 	vmw_user_bo = container_of(base, struct vmw_user_dma_buffer,
 				   prime.base);
 	(void)ttm_bo_reference(&vmw_user_bo->dma.base);
-	ttm_base_object_unref(&base);
+	if (p_base)
+		*p_base = base;
+	else
+		ttm_base_object_unref(&base);
 	*out = &vmw_user_bo->dma;
 
 	return 0;
@@ -1006,7 +1019,7 @@ int vmw_dumb_create(struct drm_file *fil
 
 	ret = vmw_user_dmabuf_alloc(dev_priv, vmw_fpriv(file_priv)->tfile,
 				    args->size, false, &args->handle,
-				    &dma_buf);
+				    &dma_buf, NULL);
 	if (unlikely(ret != 0))
 		goto out_no_dmabuf;
 
@@ -1034,7 +1047,7 @@ int vmw_dumb_map_offset(struct drm_file
 	struct vmw_dma_buffer *out_buf;
 	int ret;
 
-	ret = vmw_user_dmabuf_lookup(tfile, handle, &out_buf);
+	ret = vmw_user_dmabuf_lookup(tfile, handle, &out_buf, NULL);
 	if (ret != 0)
 		return -EINVAL;
 
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_shader.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_shader.c
@@ -470,7 +470,7 @@ int vmw_shader_define_ioctl(struct drm_d
 
 	if (arg->buffer_handle != SVGA3D_INVALID_ID) {
 		ret = vmw_user_dmabuf_lookup(tfile, arg->buffer_handle,
-					     &buffer);
+					     &buffer, NULL);
 		if (unlikely(ret != 0)) {
 			DRM_ERROR("Could not find buffer for shader "
 				  "creation.\n");
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_surface.c
@@ -43,6 +43,7 @@ struct vmw_user_surface {
 	struct vmw_surface srf;
 	uint32_t size;
 	struct drm_master *master;
+	struct ttm_base_object *backup_base;
 };
 
 /**
@@ -652,6 +653,8 @@ static void vmw_user_surface_base_releas
 	struct vmw_resource *res = &user_srf->srf.res;
 
 	*p_base = NULL;
+	if (user_srf->backup_base)
+		ttm_base_object_unref(&user_srf->backup_base);
 	vmw_resource_unreference(&res);
 }
 
@@ -846,7 +849,8 @@ int vmw_surface_define_ioctl(struct drm_
 					    res->backup_size,
 					    true,
 					    &backup_handle,
-					    &res->backup);
+					    &res->backup,
+					    &user_srf->backup_base);
 		if (unlikely(ret != 0)) {
 			vmw_resource_unreference(&res);
 			goto out_unlock;
@@ -1309,7 +1313,8 @@ int vmw_gb_surface_define_ioctl(struct d
 
 	if (req->buffer_handle != SVGA3D_INVALID_ID) {
 		ret = vmw_user_dmabuf_lookup(tfile, req->buffer_handle,
-					     &res->backup);
+					     &res->backup,
+					     &user_srf->backup_base);
 	} else if (req->drm_surface_flags &
 		   drm_vmw_surface_flag_create_buffer)
 		ret = vmw_user_dmabuf_alloc(dev_priv, tfile,
@@ -1317,7 +1322,8 @@ int vmw_gb_surface_define_ioctl(struct d
 					    req->drm_surface_flags &
 					    drm_vmw_surface_flag_shareable,
 					    &backup_handle,
-					    &res->backup);
+					    &res->backup,
+					    &user_srf->backup_base);
 
 	if (unlikely(ret != 0)) {
 		vmw_resource_unreference(&res);