[PATCH] drm/vmwgfx: Fix a destoy-while-held mutex problem.

[Thomas Hellstrom <thellstrom@vmware.com>]

When validating legacy surfaces, the backup bo might be destroyed at
surface validate time. However, the kms resource validation code may have
the bo reserved, so we will destroy a locked mutex. While there shouldn't
be any other users of that mutex when it is destroyed, it causes a lock
leak and thus throws a lockdep error.

Fix this by having the kms resource validation code hold a reference to
the bo while we have it reserved. We do this by introducing a validation
context which might come in handy when the kms code is extended to validate
multiple resources or buffers.

Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c  | 28 +++++++++++++++++++---------
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.h  | 12 +++++++++---
 drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c |  5 +++--
 drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c |  5 +++--
 4 files changed, 34 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index b3d62aa01a9b..3c824fd7cbf3 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -31,7 +31,6 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_rect.h>
 
-
 /* Might need a hrtimer here? */
 #define VMWGFX_PRESENT_RATE ((HZ / 60 > 0) ? HZ / 60 : 1)
 
@@ -2517,9 +2516,12 @@ void vmw_kms_helper_buffer_finish(struct vmw_private *dev_priv,
  * Helper to be used if an error forces the caller to undo the actions of
  * vmw_kms_helper_resource_prepare.
  */
-void vmw_kms_helper_resource_revert(struct vmw_resource *res)
+void vmw_kms_helper_resource_revert(struct vmw_validation_ctx *ctx)
 {
-	vmw_kms_helper_buffer_revert(res->backup);
+	struct vmw_resource *res = ctx->res;
+
+	vmw_kms_helper_buffer_revert(ctx->buf);
+	vmw_dmabuf_unreference(&ctx->buf);
 	vmw_resource_unreserve(res, false, NULL, 0);
 	mutex_unlock(&res->dev_priv->cmdbuf_mutex);
 }
@@ -2536,10 +2538,14 @@ void vmw_kms_helper_resource_revert(struct vmw_resource *res)
  * interrupted by a signal.
  */
 int vmw_kms_helper_resource_prepare(struct vmw_resource *res,
-				    bool interruptible)
+				    bool interruptible,
+				    struct vmw_validation_ctx *ctx)
 {
 	int ret = 0;
 
+	ctx->buf = NULL;
+	ctx->res = res;
+
 	if (interruptible)
 		ret = mutex_lock_interruptible(&res->dev_priv->cmdbuf_mutex);
 	else
@@ -2558,6 +2564,8 @@ int vmw_kms_helper_resource_prepare(struct vmw_resource *res,
 						    res->dev_priv->has_mob);
 		if (ret)
 			goto out_unreserve;
+
+		ctx->buf = vmw_dmabuf_reference(res->backup);
 	}
 	ret = vmw_resource_validate(res);
 	if (ret)
@@ -2565,7 +2573,7 @@ int vmw_kms_helper_resource_prepare(struct vmw_resource *res,
 	return 0;
 
 out_revert:
-	vmw_kms_helper_buffer_revert(res->backup);
+	vmw_kms_helper_buffer_revert(ctx->buf);
 out_unreserve:
 	vmw_resource_unreserve(res, false, NULL, 0);
 out_unlock:
@@ -2581,11 +2589,13 @@ int vmw_kms_helper_resource_prepare(struct vmw_resource *res,
  * @out_fence: Optional pointer to a fence pointer. If non-NULL, a
  * ref-counted fence pointer is returned here.
  */
-void vmw_kms_helper_resource_finish(struct vmw_resource *res,
-			     struct vmw_fence_obj **out_fence)
+void vmw_kms_helper_resource_finish(struct vmw_validation_ctx *ctx,
+				    struct vmw_fence_obj **out_fence)
 {
-	if (res->backup || out_fence)
-		vmw_kms_helper_buffer_finish(res->dev_priv, NULL, res->backup,
+	struct vmw_resource *res = ctx->res;
+
+	if (ctx->buf || out_fence)
+		vmw_kms_helper_buffer_finish(res->dev_priv, NULL, ctx->buf,
 					     out_fence, NULL);
 
 	vmw_resource_unreserve(res, false, NULL, 0);
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.h b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.h
index 948362c43c73..3d2ca280eaa7 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.h
@@ -240,6 +240,11 @@ struct vmw_display_unit {
 	int set_gui_y;
 };
 
+struct vmw_validation_ctx {
+	struct vmw_resource *res;
+	struct vmw_dma_buffer *buf;
+};
+
 #define vmw_crtc_to_du(x) \
 	container_of(x, struct vmw_display_unit, crtc)
 #define vmw_connector_to_du(x) \
@@ -296,9 +301,10 @@ void vmw_kms_helper_buffer_finish(struct vmw_private *dev_priv,
 				  struct drm_vmw_fence_rep __user *
 				  user_fence_rep);
 int vmw_kms_helper_resource_prepare(struct vmw_resource *res,
-				    bool interruptible);
-void vmw_kms_helper_resource_revert(struct vmw_resource *res);
-void vmw_kms_helper_resource_finish(struct vmw_resource *res,
+				    bool interruptible,
+				    struct vmw_validation_ctx *ctx);
+void vmw_kms_helper_resource_revert(struct vmw_validation_ctx *ctx);
+void vmw_kms_helper_resource_finish(struct vmw_validation_ctx *ctx,
 				    struct vmw_fence_obj **out_fence);
 int vmw_kms_readback(struct vmw_private *dev_priv,
 		     struct drm_file *file_priv,
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c b/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c
index 63a4cd794b73..3ec9eae831b8 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c
@@ -909,12 +909,13 @@ int vmw_kms_sou_do_surface_dirty(struct vmw_private *dev_priv,
 	struct vmw_framebuffer_surface *vfbs =
 		container_of(framebuffer, typeof(*vfbs), base);
 	struct vmw_kms_sou_surface_dirty sdirty;
+	struct vmw_validation_ctx ctx;
 	int ret;
 
 	if (!srf)
 		srf = &vfbs->surface->res;
 
-	ret = vmw_kms_helper_resource_prepare(srf, true);
+	ret = vmw_kms_helper_resource_prepare(srf, true, &ctx);
 	if (ret)
 		return ret;
 
@@ -933,7 +934,7 @@ int vmw_kms_sou_do_surface_dirty(struct vmw_private *dev_priv,
 	ret = vmw_kms_helper_dirty(dev_priv, framebuffer, clips, vclips,
 				   dest_x, dest_y, num_clips, inc,
 				   &sdirty.base);
-	vmw_kms_helper_resource_finish(srf, out_fence);
+	vmw_kms_helper_resource_finish(&ctx, out_fence);
 
 	return ret;
 }
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c b/drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c
index b68d74888ab1..6b969e5dea2a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c
@@ -980,12 +980,13 @@ int vmw_kms_stdu_surface_dirty(struct vmw_private *dev_priv,
 	struct vmw_framebuffer_surface *vfbs =
 		container_of(framebuffer, typeof(*vfbs), base);
 	struct vmw_stdu_dirty sdirty;
+	struct vmw_validation_ctx ctx;
 	int ret;
 
 	if (!srf)
 		srf = &vfbs->surface->res;
 
-	ret = vmw_kms_helper_resource_prepare(srf, true);
+	ret = vmw_kms_helper_resource_prepare(srf, true, &ctx);
 	if (ret)
 		return ret;
 
@@ -1008,7 +1009,7 @@ int vmw_kms_stdu_surface_dirty(struct vmw_private *dev_priv,
 				   dest_x, dest_y, num_clips, inc,
 				   &sdirty.base);
 out_finish:
-	vmw_kms_helper_resource_finish(srf, out_fence);
+	vmw_kms_helper_resource_finish(&ctx, out_fence);
 
 	return ret;
 }
-- 
2.14.3