1 files changed, 133 insertions, 82 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index de2c11dae231..e85b33a92624 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -489,6 +489,14 @@ void kvm_destroy_vcpus(struct kvm *kvm)
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		kvm_vcpu_destroy(vcpu);
 		xa_erase(&kvm->vcpu_array, i);
+
+		/*
+		 * Assert that the vCPU isn't visible in any way, to ensure KVM
+		 * doesn't trigger a use-after-free if destroying vCPUs results
+		 * in VM-wide request, e.g. to flush remote TLBs when tearing
+		 * down MMUs, or to mark the VM dead if a KVM_BUG_ON() fires.
+		 */
+		WARN_ON_ONCE(xa_load(&kvm->vcpu_array, i) || kvm_get_vcpu(kvm, i));
 	}
 
 	atomic_set(&kvm->online_vcpus, 0);
@@ -517,6 +525,7 @@ struct kvm_mmu_notifier_range {
 	on_lock_fn_t on_lock;
 	bool flush_on_ret;
 	bool may_block;
+	bool lockless;
 };
 
 /*
@@ -551,8 +560,8 @@ static void kvm_null_fn(void)
 	     node;							     \
 	     node = interval_tree_iter_next(node, start, last))	     \
 
-static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
-							   const struct kvm_mmu_notifier_range *range)
+static __always_inline kvm_mn_ret_t kvm_handle_hva_range(struct kvm *kvm,
+							 const struct kvm_mmu_notifier_range *range)
 {
 	struct kvm_mmu_notifier_return r = {
 		.ret = false,
@@ -571,6 +580,10 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
 			 IS_KVM_NULL_FN(range->handler)))
 		return r;
 
+	/* on_lock will never be called for lockless walks */
+	if (WARN_ON_ONCE(range->lockless && !IS_KVM_NULL_FN(range->on_lock)))
+		return r;
+
 	idx = srcu_read_lock(&kvm->srcu);
 
 	for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
@@ -594,6 +607,11 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
 			 */
 			gfn_range.arg = range->arg;
 			gfn_range.may_block = range->may_block;
+			/*
+			 * HVA-based notifications aren't relevant to private
+			 * mappings as they don't have a userspace mapping.
+			 */
+			gfn_range.attr_filter = KVM_FILTER_SHARED;
 
 			/*
 			 * {gfn(page) | page intersects with [hva_start, hva_end)} =
@@ -602,15 +620,18 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
 			gfn_range.start = hva_to_gfn_memslot(hva_start, slot);
 			gfn_range.end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, slot);
 			gfn_range.slot = slot;
+			gfn_range.lockless = range->lockless;
 
 			if (!r.found_memslot) {
 				r.found_memslot = true;
-				KVM_MMU_LOCK(kvm);
-				if (!IS_KVM_NULL_FN(range->on_lock))
-					range->on_lock(kvm);
-
-				if (IS_KVM_NULL_FN(range->handler))
-					goto mmu_unlock;
+				if (!range->lockless) {
+					KVM_MMU_LOCK(kvm);
+					if (!IS_KVM_NULL_FN(range->on_lock))
+						range->on_lock(kvm);
+
+					if (IS_KVM_NULL_FN(range->handler))
+						goto mmu_unlock;
+				}
 			}
 			r.ret |= range->handler(kvm, &gfn_range);
 		}
@@ -620,7 +641,7 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
 		kvm_flush_remote_tlbs(kvm);
 
 mmu_unlock:
-	if (r.found_memslot)
+	if (r.found_memslot && !range->lockless)
 		KVM_MMU_UNLOCK(kvm);
 
 	srcu_read_unlock(&kvm->srcu, idx);
@@ -628,7 +649,7 @@ mmu_unlock:
 	return r;
 }
 
-static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
+static __always_inline int kvm_age_hva_range(struct mmu_notifier *mn,
 						unsigned long start,
 						unsigned long end,
 						gfn_handler_t handler,
@@ -642,17 +663,18 @@ static __always_inline int kvm_handle_hva_range(struct mmu_notifier *mn,
 		.on_lock	= (void *)kvm_null_fn,
 		.flush_on_ret	= flush_on_ret,
 		.may_block	= false,
+		.lockless	= IS_ENABLED(CONFIG_KVM_MMU_LOCKLESS_AGING),
 	};
 
-	return __kvm_handle_hva_range(kvm, &range).ret;
+	return kvm_handle_hva_range(kvm, &range).ret;
 }
 
-static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn,
-							 unsigned long start,
-							 unsigned long end,
-							 gfn_handler_t handler)
+static __always_inline int kvm_age_hva_range_no_flush(struct mmu_notifier *mn,
+						      unsigned long start,
+						      unsigned long end,
+						      gfn_handler_t handler)
 {
-	return kvm_handle_hva_range(mn, start, end, handler, false);
+	return kvm_age_hva_range(mn, start, end, handler, false);
 }
 
 void kvm_mmu_invalidate_begin(struct kvm *kvm)
@@ -747,7 +769,7 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
 	 * that guest memory has been reclaimed.  This needs to be done *after*
 	 * dropping mmu_lock, as x86's reclaim path is slooooow.
 	 */
-	if (__kvm_handle_hva_range(kvm, &hva_range).found_memslot)
+	if (kvm_handle_hva_range(kvm, &hva_range).found_memslot)
 		kvm_arch_guest_memory_reclaimed(kvm);
 
 	return 0;
@@ -793,7 +815,7 @@ static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
 	};
 	bool wake;
 
-	__kvm_handle_hva_range(kvm, &hva_range);
+	kvm_handle_hva_range(kvm, &hva_range);
 
 	/* Pairs with the increment in range_start(). */
 	spin_lock(&kvm->mn_invalidate_lock);
@@ -817,8 +839,8 @@ static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
 {
 	trace_kvm_age_hva(start, end);
 
-	return kvm_handle_hva_range(mn, start, end, kvm_age_gfn,
-				    !IS_ENABLED(CONFIG_KVM_ELIDE_TLB_FLUSH_IF_YOUNG));
+	return kvm_age_hva_range(mn, start, end, kvm_age_gfn,
+				 !IS_ENABLED(CONFIG_KVM_ELIDE_TLB_FLUSH_IF_YOUNG));
 }
 
 static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
@@ -841,7 +863,7 @@ static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
 	 * cadence. If we find this inaccurate, we might come up with a
 	 * more sophisticated heuristic later.
 	 */
-	return kvm_handle_hva_range_no_flush(mn, start, end, kvm_age_gfn);
+	return kvm_age_hva_range_no_flush(mn, start, end, kvm_age_gfn);
 }
 
 static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
@@ -850,8 +872,8 @@ static int kvm_mmu_notifier_test_young(struct mmu_notifier *mn,
 {
 	trace_kvm_test_age_hva(address);
 
-	return kvm_handle_hva_range_no_flush(mn, address, address + 1,
-					     kvm_test_age_gfn);
+	return kvm_age_hva_range_no_flush(mn, address, address + 1,
+					  kvm_test_age_gfn);
 }
 
 static void kvm_mmu_notifier_release(struct mmu_notifier *mn,
@@ -1066,15 +1088,6 @@ out_err:
 }
 
 /*
- * Called after the VM is otherwise initialized, but just before adding it to
- * the vm_list.
- */
-int __weak kvm_arch_post_init_vm(struct kvm *kvm)
-{
-	return 0;
-}
-
-/*
  * Called just after removing the VM from the vm_list, but before doing any
  * other destruction.
  */
@@ -1194,10 +1207,6 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
 	if (r)
 		goto out_err_no_debugfs;
 
-	r = kvm_arch_post_init_vm(kvm);
-	if (r)
-		goto out_err;
-
 	mutex_lock(&kvm_lock);
 	list_add(&kvm->vm_list, &vm_list);
 	mutex_unlock(&kvm_lock);
@@ -1207,8 +1216,6 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
 
 	return kvm;
 
-out_err:
-	kvm_destroy_vm_debugfs(kvm);
 out_err_no_debugfs:
 	kvm_coalesced_mmio_free(kvm);
 out_no_coalesced_mmio:
@@ -1264,7 +1271,6 @@ static void kvm_destroy_vm(struct kvm *kvm)
 	kvm_destroy_pm_notifier(kvm);
 	kvm_uevent_notify_change(KVM_EVENT_DESTROY_VM, kvm);
 	kvm_destroy_vm_debugfs(kvm);
-	kvm_arch_sync_events(kvm);
 	mutex_lock(&kvm_lock);
 	list_del(&kvm->vm_list);
 	mutex_unlock(&kvm_lock);
@@ -1926,16 +1932,8 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
 	return false;
 }
 
-/*
- * Allocate some memory and give it an address in the guest physical address
- * space.
- *
- * Discontiguous memory is allowed, mostly for framebuffers.
- *
- * Must be called holding kvm->slots_lock for write.
- */
-int __kvm_set_memory_region(struct kvm *kvm,
-			    const struct kvm_userspace_memory_region2 *mem)
+static int kvm_set_memory_region(struct kvm *kvm,
+				 const struct kvm_userspace_memory_region2 *mem)
 {
 	struct kvm_memory_slot *old, *new;
 	struct kvm_memslots *slots;
@@ -1945,6 +1943,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	int as_id, id;
 	int r;
 
+	lockdep_assert_held(&kvm->slots_lock);
+
 	r = check_memory_region_flags(kvm, mem);
 	if (r)
 		return r;
@@ -1972,7 +1972,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		return -EINVAL;
 	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
 		return -EINVAL;
-	if ((mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
+
+	/*
+	 * The size of userspace-defined memory regions is restricted in order
+	 * to play nice with dirty bitmap operations, which are indexed with an
+	 * "unsigned int".  KVM's internal memory regions don't support dirty
+	 * logging, and so are exempt.
+	 */
+	if (id < KVM_USER_MEM_SLOTS &&
+	    (mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
 		return -EINVAL;
 
 	slots = __kvm_memslots(kvm, as_id);
@@ -2056,19 +2064,19 @@ out:
 	kfree(new);
 	return r;
 }
-EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
 
-int kvm_set_memory_region(struct kvm *kvm,
-			  const struct kvm_userspace_memory_region2 *mem)
+int kvm_set_internal_memslot(struct kvm *kvm,
+			     const struct kvm_userspace_memory_region2 *mem)
 {
-	int r;
+	if (WARN_ON_ONCE(mem->slot < KVM_USER_MEM_SLOTS))
+		return -EINVAL;
 
-	mutex_lock(&kvm->slots_lock);
-	r = __kvm_set_memory_region(kvm, mem);
-	mutex_unlock(&kvm->slots_lock);
-	return r;
+	if (WARN_ON_ONCE(mem->flags))
+		return -EINVAL;
+
+	return kvm_set_memory_region(kvm, mem);
 }
-EXPORT_SYMBOL_GPL(kvm_set_memory_region);
+EXPORT_SYMBOL_GPL(kvm_set_internal_memslot);
 
 static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 					  struct kvm_userspace_memory_region2 *mem)
@@ -2076,6 +2084,7 @@ static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
 	if ((u16)mem->slot >= KVM_USER_MEM_SLOTS)
 		return -EINVAL;
 
+	guard(mutex)(&kvm->slots_lock);
 	return kvm_set_memory_region(kvm, mem);
 }
 
@@ -2408,6 +2417,14 @@ static __always_inline void kvm_handle_gfn_range(struct kvm *kvm,
 	gfn_range.arg = range->arg;
 	gfn_range.may_block = range->may_block;
 
+	/*
+	 * If/when KVM supports more attributes beyond private .vs shared, this
+	 * _could_ set KVM_FILTER_{SHARED,PRIVATE} appropriately if the entire target
+	 * range already has the desired private vs. shared state (it's unclear
+	 * if that is a net win).  For now, KVM reaches this point if and only
+	 * if the private flag is being toggled, i.e. all mappings are in play.
+	 */
+
 	for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
 		slots = __kvm_memslots(kvm, i);
 
@@ -2464,6 +2481,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
 	struct kvm_mmu_notifier_range pre_set_range = {
 		.start = start,
 		.end = end,
+		.arg.attributes = attributes,
 		.handler = kvm_pre_set_memory_attributes,
 		.on_lock = kvm_mmu_invalidate_begin,
 		.flush_on_ret = true,
@@ -4116,32 +4134,30 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id)
 
 	mutex_lock(&kvm->lock);
 
-#ifdef CONFIG_LOCKDEP
-	/* Ensure that lockdep knows vcpu->mutex is taken *inside* kvm->lock */
-	mutex_lock(&vcpu->mutex);
-	mutex_unlock(&vcpu->mutex);
-#endif
-
 	if (kvm_get_vcpu_by_id(kvm, id)) {
 		r = -EEXIST;
 		goto unlock_vcpu_destroy;
 	}
 
 	vcpu->vcpu_idx = atomic_read(&kvm->online_vcpus);
-	r = xa_reserve(&kvm->vcpu_array, vcpu->vcpu_idx, GFP_KERNEL_ACCOUNT);
+	r = xa_insert(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, GFP_KERNEL_ACCOUNT);
+	WARN_ON_ONCE(r == -EBUSY);
 	if (r)
 		goto unlock_vcpu_destroy;
 
-	/* Now it's all set up, let userspace reach it */
+	/*
+	 * Now it's all set up, let userspace reach it.  Grab the vCPU's mutex
+	 * so that userspace can't invoke vCPU ioctl()s until the vCPU is fully
+	 * visible (per online_vcpus), e.g. so that KVM doesn't get tricked
+	 * into a NULL-pointer dereference because KVM thinks the _current_
+	 * vCPU doesn't exist.  As a bonus, taking vcpu->mutex ensures lockdep
+	 * knows it's taken *inside* kvm->lock.
+	 */
+	mutex_lock(&vcpu->mutex);
 	kvm_get_kvm(kvm);
 	r = create_vcpu_fd(vcpu);
 	if (r < 0)
-		goto kvm_put_xa_release;
-
-	if (KVM_BUG_ON(xa_store(&kvm->vcpu_array, vcpu->vcpu_idx, vcpu, 0), kvm)) {
-		r = -EINVAL;
-		goto kvm_put_xa_release;
-	}
+		goto kvm_put_xa_erase;
 
 	/*
 	 * Pairs with smp_rmb() in kvm_get_vcpu.  Store the vcpu
@@ -4149,15 +4165,17 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, unsigned long id)
 	 */
 	smp_wmb();
 	atomic_inc(&kvm->online_vcpus);
+	mutex_unlock(&vcpu->mutex);
 
 	mutex_unlock(&kvm->lock);
 	kvm_arch_vcpu_postcreate(vcpu);
 	kvm_create_vcpu_debugfs(vcpu);
 	return r;
 
-kvm_put_xa_release:
+kvm_put_xa_erase:
+	mutex_unlock(&vcpu->mutex);
 	kvm_put_kvm_no_destroy(kvm);
-	xa_release(&kvm->vcpu_array, vcpu->vcpu_idx);
+	xa_erase(&kvm->vcpu_array, vcpu->vcpu_idx);
 unlock_vcpu_destroy:
 	mutex_unlock(&kvm->lock);
 	kvm_dirty_ring_free(&vcpu->dirty_ring);
@@ -4222,15 +4240,14 @@ static int kvm_vcpu_ioctl_get_stats_fd(struct kvm_vcpu *vcpu)
 	if (fd < 0)
 		return fd;
 
-	file = anon_inode_getfile(name, &kvm_vcpu_stats_fops, vcpu, O_RDONLY);
+	file = anon_inode_getfile_fmode(name, &kvm_vcpu_stats_fops, vcpu,
+					O_RDONLY, FMODE_PREAD);
 	if (IS_ERR(file)) {
 		put_unused_fd(fd);
 		return PTR_ERR(file);
 	}
 
 	kvm_get_kvm(vcpu->kvm);
-
-	file->f_mode |= FMODE_PREAD;
 	fd_install(fd, file);
 
 	return fd;
@@ -4282,6 +4299,33 @@ static int kvm_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
 }
 #endif
 
+static int kvm_wait_for_vcpu_online(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+
+	/*
+	 * In practice, this happy path will always be taken, as a well-behaved
+	 * VMM will never invoke a vCPU ioctl() before KVM_CREATE_VCPU returns.
+	 */
+	if (likely(vcpu->vcpu_idx < atomic_read(&kvm->online_vcpus)))
+		return 0;
+
+	/*
+	 * Acquire and release the vCPU's mutex to wait for vCPU creation to
+	 * complete (kvm_vm_ioctl_create_vcpu() holds the mutex until the vCPU
+	 * is fully online).
+	 */
+	if (mutex_lock_killable(&vcpu->mutex))
+		return -EINTR;
+
+	mutex_unlock(&vcpu->mutex);
+
+	if (WARN_ON_ONCE(!kvm_get_vcpu(kvm, vcpu->vcpu_idx)))
+		return -EIO;
+
+	return 0;
+}
+
 static long kvm_vcpu_ioctl(struct file *filp,
 			   unsigned int ioctl, unsigned long arg)
 {
@@ -4298,6 +4342,15 @@ static long kvm_vcpu_ioctl(struct file *filp,
 		return -EINVAL;
 
 	/*
+	 * Wait for the vCPU to be online before handling the ioctl(), as KVM
+	 * assumes the vCPU is reachable via vcpu_array, i.e. may dereference
+	 * a NULL pointer if userspace invokes an ioctl() before KVM is ready.
+	 */
+	r = kvm_wait_for_vcpu_online(vcpu);
+	if (r)
+		return r;
+
+	/*
 	 * Some architectures have vcpu ioctls that are asynchronous to vcpu
 	 * execution; mutex_lock() would break them.
 	 */
@@ -4982,16 +5035,14 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
 	if (fd < 0)
 		return fd;
 
-	file = anon_inode_getfile("kvm-vm-stats",
-			&kvm_vm_stats_fops, kvm, O_RDONLY);
+	file = anon_inode_getfile_fmode("kvm-vm-stats",
+			&kvm_vm_stats_fops, kvm, O_RDONLY, FMODE_PREAD);
 	if (IS_ERR(file)) {
 		put_unused_fd(fd);
 		return PTR_ERR(file);
 	}
 
 	kvm_get_kvm(kvm);
-
-	file->f_mode |= FMODE_PREAD;
 	fd_install(fd, file);
 
 	return fd;