[PATCH 02/12] drm/vmwgfx: reject DX_BIND_QUERY without a DX context

[Zack Rusin <zack.rusin@broadcom.com>]

vmw_cmd_dx_bind_query() unconditionally dereferences
sw_context->dx_ctx_node->ctx.  Userspace can trigger a NULL pointer
dereference from any render-node fd by submitting an execbuf with
dx_context_handle == SVGA3D_INVALID_ID and a SVGA_3D_CMD_DX_BIND_QUERY
opcode in the command stream: dx_ctx_node is left NULL and the kernel
oopses on the assignment.  The same NULL is then re-read in
vmw_resources_reserve() via vmw_context_get_dx_query_mob().

All sibling DX handlers fail-close on a missing dx_ctx_node using
VMW_GET_CTX_NODE().  Use the same pattern here, returning -EINVAL up
front before any relocation state is published.

Fixes: 9c079b8ce8bf ("drm/vmwgfx: Adapt execbuf to the new validation api")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index e1f18020170a..b07f052474d0 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -1272,9 +1272,13 @@ static int vmw_cmd_dx_bind_query(struct vmw_private *dev_priv,
 				 SVGA3dCmdHeader *header)
 {
 	VMW_DECLARE_CMD_VAR(*cmd, SVGA3dCmdDXBindQuery);
+	struct vmw_ctx_validation_info *ctx_node = VMW_GET_CTX_NODE(sw_context);
 	struct vmw_bo *vmw_bo;
 	int ret;
 
+	if (!ctx_node)
+		return -EINVAL;
+
 	cmd = container_of(header, typeof(*cmd), header);
 
 	/*
@@ -1288,7 +1292,7 @@ static int vmw_cmd_dx_bind_query(struct vmw_private *dev_priv,
 		return ret;
 
 	sw_context->dx_query_mob = vmw_bo;
-	sw_context->dx_query_ctx = sw_context->dx_ctx_node->ctx;
+	sw_context->dx_query_ctx = ctx_node->ctx;
 	return 0;
 }
 
-- 
2.51.0