CVE-2022-50044: Concurrent Execution using Shared Resource with Improper Synchronization

In the Linux kernel, the following vulnerability has been resolved:

net: qrtr: start MHI channel after endpoit creation

MHI channel may generates event/interrupt right after enabling. It may leads to 2 race conditions issues.

1) Such event may be dropped by qcom_mhi_qrtr_dl_callback() at check:

if (!qdev || mhi_res->transaction_status) return;

Because dev_set_drvdata(&mhi_dev->dev, qdev) may be not performed at this moment. In this situation qrtr-ns will be unable to enumerate services in device. ---------------------------------------------------------------

2) Such event may come at the moment after dev_set_drvdata() and before qrtr_endpoint_register(). In this case kernel will panic with accessing wrong pointer at qcom_mhi_qrtr_dl_callback():

rc = qrtr_endpoint_post(&qdev->ep, mhi_res->buf_addr, mhi_res->bytes_xferd);

Because endpoint is not created yet. -------------------------------------------------------------- So move mhi_prepare_for_transfer_autoqueue after endpoint creation to fix it.