6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Robin Murphy robin.murphy@arm.com
commit b46064a18810bad3aea089a79993ca5ea7a3d2b2 upstream.
It turns out that deferred default domain creation leaves a subtle race window during iommu_device_register() wherein a client driver may asynchronously probe in parallel and get as far as performing DMA API operations with dma-direct, only to be switched to iommu-dma underfoot once the default domain attachment finally happens, with obviously disastrous consequences. Even the wonky of_iommu_configure() path is at risk, since iommu_fwspec_init() will no longer defer client probe as the instance ops are (necessarily) already registered, and the "replay" iommu_probe_device() call can see dev->iommu_group already set and so think there's nothing to do either.
Fortunately we already have the right tool in the right place in the form of iommu_device_use_default_domain(), which just needs to ensure that said default domain is actually ready to *be* used. Deferring the client probe shouldn't have too much impact, given that this only happens while the IOMMU driver is probing, and thus due to kick the deferred probe list again once it finishes.
Reported-by: Charan Teja Kalla quic_charante@quicinc.com Fixes: 98ac73f99bc4 ("iommu: Require a default_domain for all iommu drivers") Reviewed-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/e88b94c9b575034a2c98a48b3d383654cbda7902.174075326... Signed-off-by: Joerg Roedel jroedel@suse.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iommu/iommu.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -3115,6 +3115,11 @@ int iommu_device_use_default_domain(stru return 0;
mutex_lock(&group->mutex); + /* We may race against bus_iommu_probe() finalising groups here */ + if (!group->default_domain) { + ret = -EPROBE_DEFER; + goto unlock_out; + } if (group->owner_cnt) { if (group->domain != group->default_domain || group->owner || !xa_empty(&group->pasid_array)) {