On Thu, Jan 22, 2026 at 12:32:03PM +0100, Christian König wrote: > >> What roughly happens is that each DMA-buf mapping through a couple > >> of hoops keeps a reference on the device, so even after a hotplug > >> event the device can only fully go away after all housekeeping > >> structures are destroyed and buffers freed. > > > > A simple reference on the device means nothing for these kinds of > > questions. It does not stop unloading and reloading a driver. > > Well as far as I know it stops the PCIe address space from being re-used. > > So when you do an "echo 1 > remove" and then an re-scan on the > upstream bridge that works, but you get different addresses for your > MMIO BARs!
That's pretty a niche scenario.. Most people don't rescan their PCI bus. If you just do rmmod/insmod then it will be re-used, there is no rescan to move the MMIO around on that case. > Oh, well I never looked to deeply into that. > > As far as I know it doesn't block, but rather the last drm_dev_put() > just cleans things up. > > And we have a CI test system which exercises that stuff over and > over again because we have a big customer depending on that. I doubt a CI would detect a UAF like we are discussing here.. Connect a RDMA pinned importer. Do rmmod. If rmmod doesn't hang the driver has a UAF on some RAS cases. Not great, but is unlikely to actually trouble any real user. Jason
