On Tue, Mar 07, 2017 at 11:12:43PM -0500, Hon Ching(Vicky) Lo wrote: > On Mon, 2017-03-06 at 16:19 -0700, Jason Gunthorpe wrote:
> > Also, how does locking work here? Does the vio core prevent > > tpm_ibmvtpm_get_desired_dma and tpm_ibmvtpm_remove from running > > concurrently? > > No, vio core doesn't prevent tpm_ibmvtpm_get_desired_dma and > tpm_ibmvtpm_remove > from running concurrently. > > vio_bus_probe calls vio_cmo_bus_probe which calls tpm_ibmvtpm_get_desired_dma. > tpm_ibmvtpm_get_desired_dma is called before the code enters critical section. > > There is no locking mechanism around tpm_ibmvtpm_remove in vio_bus_remove. > > What's the concern here? tpm_ibmvtpm_remove makes the pointer that tpm_ibmvtpm_get_desired_dma is accessing invalid, so some kind of locking is technically required so that the two things do not create a use after free race: > > + /* For tpm_ibmvtpm_get_desired_dma */ > > + dev_set_drvdata(&vdev->dev, NULL); > > kfree(ibmvtpm); Eg with the kfree above. It may be that the driver core prevents probe/remove from running concurrently and things are fine, but this is something to confirm.. Jason
