From 9e0f4f2918c2ff145d3dedee862d9919a6ed5812 Mon Sep 17 00:00:00 2001 From: Dmitry Torokhov Date: Fri, 14 Jul 2023 15:45:32 -0700 Subject: kvm/vfio: ensure kvg instance stays around in kvm_vfio_group_add() kvm_vfio_group_add() creates kvg instance, links it to kv->group_list, and calls kvm_vfio_file_set_kvm() with kvg->file as an argument after dropping kv->lock. If we race group addition and deletion calls, kvg instance may get freed by the time we get around to calling kvm_vfio_file_set_kvm(). Previous iterations of the code did not reference kvg->file outside of the critical section, but used a temporary variable. Still, they had similar problem of the file reference being owned by kvg structure and potential for kvm_vfio_group_del() dropping it before kvm_vfio_group_add() had a chance to complete. Fix this by moving call to kvm_vfio_file_set_kvm() under the protection of kv->lock. We already call it while holding the same lock when vfio group is being deleted, so it should be safe here as well. Fixes: 2fc1bec15883 ("kvm: set/clear kvm to/from vfio_group when group add/delete") Reviewed-by: Alex Williamson Signed-off-by: Dmitry Torokhov Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20230714224538.404793-1-dmitry.torokhov@gmail.com Signed-off-by: Alex Williamson --- virt/kvm/vfio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'virt') diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c index 07cb5f44b2a2..59945f6001f4 100644 --- a/virt/kvm/vfio.c +++ b/virt/kvm/vfio.c @@ -180,10 +180,10 @@ static int kvm_vfio_file_add(struct kvm_device *dev, unsigned int fd) list_add_tail(&kvf->node, &kv->file_list); kvm_arch_start_assignment(dev->kvm); + kvm_vfio_file_set_kvm(kvf->file, dev->kvm); mutex_unlock(&kv->lock); - kvm_vfio_file_set_kvm(kvf->file, dev->kvm); kvm_vfio_update_coherency(dev); return 0; -- cgit