habanalabs: fix dma-buf release handling if dma_buf_fd() fails

The dma-buf private object is freed if a call to dma_buf_fd() fails,
and because a file was already associated with the dma-buf in
dma_buf_export(), the release op will be called and will use this
object.

Mark the 'priv' field as NULL in this case, and avoid accessing it from
the release op.
Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>

drivers/misc/habanalabs/common/memory.c

@@ -1782,7 +1782,12 @@ static void hl_unmap_dmabuf(struct dma_buf_attachment *attachment,
 static void hl_release_dmabuf(struct dma_buf *dmabuf)
 {
 	struct hl_dmabuf_priv *hl_dmabuf = dmabuf->priv;
-	struct hl_ctx *ctx = hl_dmabuf->ctx;
+	struct hl_ctx *ctx;
+
+	if (!hl_dmabuf)
+		return;
+
+	ctx = hl_dmabuf->ctx;
 
 	if (hl_dmabuf->memhash_hnode) {
 		mutex_lock(&ctx->mem_hash_lock);
@@ -1822,7 +1827,7 @@ static int export_dmabuf(struct hl_ctx *ctx,
 
 	fd = dma_buf_fd(hl_dmabuf->dmabuf, flags);
 	if (fd < 0) {
-		dev_err(hdev->dev, "failed to get a file descriptor for a dma-buf\n");
+		dev_err(hdev->dev, "failed to get a file descriptor for a dma-buf, %d\n", fd);
 		rc = fd;
 		goto err_dma_buf_put;
 	}
@@ -1835,6 +1840,7 @@ static int export_dmabuf(struct hl_ctx *ctx,
 	return 0;
 
 err_dma_buf_put:
+	hl_dmabuf->dmabuf->priv = NULL;
 	dma_buf_put(hl_dmabuf->dmabuf);
 	return rc;
 }