6.5-stable review patch. If anyone has any objections, please let me know.
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From: Dmitry Torokhov dmitry.torokhov@gmail.com
[ Upstream commit 9e0f4f2918c2ff145d3dedee862d9919a6ed5812 ]
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 alex.williamson@redhat.com Signed-off-by: Dmitry Torokhov dmitry.torokhov@gmail.com Reviewed-by: Kevin Tian kevin.tian@intel.com Link: https://lore.kernel.org/r/20230714224538.404793-1-dmitry.torokhov@gmail.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- virt/kvm/vfio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c index af3d0cf06e4c6..365d30779768a 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;