On Tue, Jun 10, 2025 at 03:40:40PM +0100, Robin Murphy wrote: > On 2025-06-10 2:04 pm, Jason Gunthorpe wrote: > > On Tue, Jun 10, 2025 at 12:07:00AM -0700, Nicolin Chen wrote: > > > On Tue, Jun 10, 2025 at 12:26:07PM +0800, Baolu Lu wrote: > > > > On 6/10/25 02:45, Nicolin Chen wrote: > > > > > + ops = dev_iommu_ops(dev); > > > > > > > > Should this be protected by group->mutext? > > > > > > Not seemingly, but should require the iommu_probe_device_lock I > > > think. > > > > group and ops are not permitted to change while a driver is attached.. > > > > IIRC the FLR code in PCI doesn't always ensure that (due to the sysfs > > paths), so yeah, this looks troubled. iommu_probe_device_lock perhaps > > would fix it. > > No, iommu_probe_device_lock is for protecting access to dev->iommu in the > probe path until the device is definitively assigned to a group (or not). > Fundamentally it defends against multiple sources triggering a probe of the > same device in parallel - once the device *is* probed it is no longer > relevant, and the group mutex is the right thing to protect all subsequent > operations. Yes, adding iommu_probe_device_lock to iommu_deinit_device() would be gross. but something is required to protect the load of dev->iommu_group.. dev->iommu_group->mutex can't protect itself against a race UAF on deinit. READ_ONCE is good enough to protect from races with the probe path, no need for iommu_probe_device_lock there. In this case need to look at the PCI sysfs for races against the iommu_release_device()/etc that is freeing the dev->iommu_group. Maybe the sysfs is always removed before we get to release. Or maybe the PCI FLR sysfs code should hold the device_lock.. Jason
