bus: mhi: pci_generic: Fix possible use-after-free in mhi_pci_remove()

This driver's remove path calls del_timer(). However, that function
does not wait until the timer handler finishes. This means that the
timer handler may still be running after the driver's remove function
has finished, which would result in a use-after-free.

Fix by calling del_timer_sync(), which makes sure the timer handler
has finished, and unable to re-schedule itself.

Link: https://lore.kernel.org/r/20210413160318.2003699-1-weiyongjun1@huawei.com
Fixes: 8562d4fe ("mhi: pci_generic: Add health-check")
Cc: stable <stable@vger.kernel.org>
Reported-by: Hulk Robot <hulkci@huawei.com>
Reviewed-by: Hemant kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20210606153741.20725-3-manivannan.sadhasivam@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/bus/mhi/pci_generic.c

@@ -708,7 +708,7 @@ static void mhi_pci_remove(struct pci_dev *pdev)
 	struct mhi_pci_device *mhi_pdev = pci_get_drvdata(pdev);
 	struct mhi_controller *mhi_cntrl = &mhi_pdev->mhi_cntrl;
 
-	del_timer(&mhi_pdev->health_check_timer);
+	del_timer_sync(&mhi_pdev->health_check_timer);
 	cancel_work_sync(&mhi_pdev->recovery_work);
 
 	if (test_and_clear_bit(MHI_PCI_DEV_STARTED, &mhi_pdev->status)) {