4.9-stable patches

added patches:
	kvm-prevent-module-exit-until-all-vms-are-freed.patch

diff --git a/queue-4.9/kvm-prevent-module-exit-until-all-vms-are-freed.patch b/queue-4.9/kvm-prevent-module-exit-until-all-vms-are-freed.patch
new file mode 100644 (file)
index 0000000..ac9cddf
--- /dev/null
+++ b/queue-4.9/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 <dmatlack@google.com>
+Date: Thu, 3 Mar 2022 18:33:27 +0000
+Subject: KVM: Prevent module exit until all VMs are freed
+
+From: David Matlack <dmatlack@google.com>
+
+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 <bgardon@google.com>
+[ Based on a patch from Ben implemented for Google's kernel. ]
+Signed-off-by: David Matlack <dmatlack@google.com>
+Message-Id: <20220303183328.1499189-2-dmatlack@google.com>
+Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ virt/kvm/kvm_main.c |   13 +++++++++++++
+ 1 file changed, 13 insertions(+)
+
+--- a/virt/kvm/kvm_main.c
++++ b/virt/kvm/kvm_main.c
+@@ -107,6 +107,8 @@ 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
+@@ -714,6 +716,16 @@ 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:
+@@ -798,6 +810,7 @@ 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-4.9/series b/queue-4.9/series
index ce54877fcc95149e660d1781d0e2e973b969e5c1..6206e9b25aba5dd5589ae85c17621e0b8930e2da 100644 (file)
--- a/queue-4.9/series
+++ b/queue-4.9/series
@@ -147,3 +147,4 @@ video-fbdev-sm712fb-fix-crash-in-smtcfb_write.patch
 media-hdpvr-initialize-dev-worker-at-hdpvr_register_.patch
 mmc-host-return-an-error-when-enable_sdio_irq-ops-is.patch
 scsi-qla2xxx-fix-incorrect-reporting-of-task-management-failure.patch
+kvm-prevent-module-exit-until-all-vms-are-freed.patch