From 7f0fa234d69167450036fe7e468f6b24d3637478 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Sun, 3 Apr 2022 08:53:56 +0200 Subject: [PATCH] 4.14-stable patches added patches: kvm-prevent-module-exit-until-all-vms-are-freed.patch --- ...-module-exit-until-all-vms-are-freed.patch | 75 +++++++++++++++++++ queue-4.14/series | 1 + 2 files changed, 76 insertions(+) create mode 100644 queue-4.14/kvm-prevent-module-exit-until-all-vms-are-freed.patch diff --git a/queue-4.14/kvm-prevent-module-exit-until-all-vms-are-freed.patch b/queue-4.14/kvm-prevent-module-exit-until-all-vms-are-freed.patch new file mode 100644 index 00000000000..d615b5c4b1d --- /dev/null +++ b/queue-4.14/kvm-prevent-module-exit-until-all-vms-are-freed.patch @@ -0,0 +1,75 @@ +From 5f6de5cbebee925a612856fce6f9182bb3eee0db Mon Sep 17 00:00:00 2001 +From: David Matlack +Date: Thu, 3 Mar 2022 18:33:27 +0000 +Subject: KVM: Prevent module exit until all VMs are freed + +From: David Matlack + +commit 5f6de5cbebee925a612856fce6f9182bb3eee0db upstream. + +Tie the lifetime the KVM module to the lifetime of each VM via +kvm.users_count. This way anything that grabs a reference to the VM via +kvm_get_kvm() cannot accidentally outlive the KVM module. + +Prior to this commit, the lifetime of the KVM module was tied to the +lifetime of /dev/kvm file descriptors, VM file descriptors, and vCPU +file descriptors by their respective file_operations "owner" field. +This approach is insufficient because references grabbed via +kvm_get_kvm() do not prevent closing any of the aforementioned file +descriptors. + +This fixes a long standing theoretical bug in KVM that at least affects +async page faults. kvm_setup_async_pf() grabs a reference via +kvm_get_kvm(), and drops it in an asynchronous work callback. Nothing +prevents the VM file descriptor from being closed and the KVM module +from being unloaded before this callback runs. + +Fixes: af585b921e5d ("KVM: Halt vcpu if page it tries to access is swapped out") +Fixes: 3d3aab1b973b ("KVM: set owner of cpu and vm file operations") +Cc: stable@vger.kernel.org +Suggested-by: Ben Gardon +[ Based on a patch from Ben implemented for Google's kernel. ] +Signed-off-by: David Matlack +Message-Id: <20220303183328.1499189-2-dmatlack@google.com> +Signed-off-by: Paolo Bonzini +Signed-off-by: Greg Kroah-Hartman +--- + virt/kvm/kvm_main.c | 13 +++++++++++++ + 1 file changed, 13 insertions(+) + +--- a/virt/kvm/kvm_main.c ++++ b/virt/kvm/kvm_main.c +@@ -112,6 +112,8 @@ EXPORT_SYMBOL_GPL(kvm_debugfs_dir); + static int kvm_debugfs_num_entries; + static const struct file_operations *stat_fops_per_vm[]; + ++static struct file_operations kvm_chardev_ops; ++ + static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl, + unsigned long arg); + #ifdef CONFIG_KVM_COMPAT +@@ -716,6 +718,16 @@ static struct kvm *kvm_create_vm(unsigne + + preempt_notifier_inc(); + ++ /* ++ * When the fd passed to this ioctl() is opened it pins the module, ++ * but try_module_get() also prevents getting a reference if the module ++ * is in MODULE_STATE_GOING (e.g. if someone ran "rmmod --wait"). ++ */ ++ if (!try_module_get(kvm_chardev_ops.owner)) { ++ r = -ENODEV; ++ goto out_err; ++ } ++ + return kvm; + + out_err: +@@ -792,6 +804,7 @@ static void kvm_destroy_vm(struct kvm *k + preempt_notifier_dec(); + hardware_disable_all(); + mmdrop(mm); ++ module_put(kvm_chardev_ops.owner); + } + + void kvm_get_kvm(struct kvm *kvm) diff --git a/queue-4.14/series b/queue-4.14/series index ec85e36e43d..7552a4fda23 100644 --- a/queue-4.14/series +++ b/queue-4.14/series @@ -186,3 +186,4 @@ powerpc-lib-sstep-fix-sthcx-instruction.patch powerpc-lib-sstep-fix-build-errors-with-newer-binutils.patch scsi-qla2xxx-fix-warning-for-missing-error-code.patch scsi-qla2xxx-suppress-a-kernel-complaint-in-qla_create_qpair.patch +kvm-prevent-module-exit-until-all-vms-are-freed.patch -- 2.47.3