Kernel: Make AnonymousVMObject physical page APIs OOM safe

AnonymousVMObject::create_with_physical_page(s) can't be NonnullRefPtr
as it allocates internally. Fixing the API then surfaced an issue in
ScatterGatherList, where the code was attempting to create an
AnonymousVMObject in the constructor which will not be observable
during OOM.

Fix all of these issues and start propagating errors at the callers
of the AnonymousVMObject and ScatterGatherList APis.

4 files changed, 15 insertions, 12 deletions

diff --git a/Kernel/VM/AnonymousVMObject.cpp b/Kernel/VM/AnonymousVMObject.cpp
index 038bae41a5..912e4cb275 100644
--- a/Kernel/VM/AnonymousVMObject.cpp
+++ b/Kernel/VM/AnonymousVMObject.cpp
@@ -60,14 +60,14 @@ RefPtr<AnonymousVMObject> AnonymousVMObject::create_with_size(size_t size, Alloc
     return adopt_ref_if_nonnull(new AnonymousVMObject(size, commit));
 }
 
-NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_physical_pages(NonnullRefPtrVector<PhysicalPage> physical_pages)
+RefPtr<AnonymousVMObject> AnonymousVMObject::create_with_physical_pages(NonnullRefPtrVector<PhysicalPage> physical_pages)
 {
-    return adopt_ref(*new AnonymousVMObject(physical_pages));
+    return adopt_ref_if_nonnull(new AnonymousVMObject(physical_pages));
 }
 
-NonnullRefPtr<AnonymousVMObject> AnonymousVMObject::create_with_physical_page(PhysicalPage& page)
+RefPtr<AnonymousVMObject> AnonymousVMObject::create_with_physical_page(PhysicalPage& page)
 {
-    return adopt_ref(*new AnonymousVMObject(page));
+    return adopt_ref_if_nonnull(new AnonymousVMObject(page));
 }
 
 RefPtr<AnonymousVMObject> AnonymousVMObject::create_for_physical_range(PhysicalAddress paddr, size_t size)
diff --git a/Kernel/VM/AnonymousVMObject.h b/Kernel/VM/AnonymousVMObject.h
index a2c990fa59..bdca7c0336 100644
--- a/Kernel/VM/AnonymousVMObject.h
+++ b/Kernel/VM/AnonymousVMObject.h
@@ -22,8 +22,8 @@ public:
 
     static RefPtr<AnonymousVMObject> create_with_size(size_t, AllocationStrategy);
     static RefPtr<AnonymousVMObject> create_for_physical_range(PhysicalAddress paddr, size_t size);
-    static NonnullRefPtr<AnonymousVMObject> create_with_physical_page(PhysicalPage& page);
-    static NonnullRefPtr<AnonymousVMObject> create_with_physical_pages(NonnullRefPtrVector<PhysicalPage>);
+    static RefPtr<AnonymousVMObject> create_with_physical_page(PhysicalPage& page);
+    static RefPtr<AnonymousVMObject> create_with_physical_pages(NonnullRefPtrVector<PhysicalPage>);
     virtual RefPtr<VMObject> clone() override;
 
     RefPtr<PhysicalPage> allocate_committed_page(size_t);
diff --git a/Kernel/VM/ScatterGatherList.cpp b/Kernel/VM/ScatterGatherList.cpp
index 6ebbfece2d..a8452de263 100644
--- a/Kernel/VM/ScatterGatherList.cpp
+++ b/Kernel/VM/ScatterGatherList.cpp
@@ -8,13 +8,16 @@
 
 namespace Kernel {
 
-NonnullRefPtr<ScatterGatherList> ScatterGatherList::create(AsyncBlockDeviceRequest& request, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size)
+RefPtr<ScatterGatherList> ScatterGatherList::create(AsyncBlockDeviceRequest& request, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size)
 {
-    return adopt_ref(*new ScatterGatherList(request, allocated_pages, device_block_size));
+    auto vm_object = AnonymousVMObject::create_with_physical_pages(allocated_pages);
+    if (!vm_object)
+        return {};
+    return adopt_ref_if_nonnull(new ScatterGatherList(vm_object.release_nonnull(), request, device_block_size));
 }
 
-ScatterGatherList::ScatterGatherList(AsyncBlockDeviceRequest& request, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size)
-    : m_vm_object(AnonymousVMObject::create_with_physical_pages(allocated_pages))
+ScatterGatherList::ScatterGatherList(NonnullRefPtr<AnonymousVMObject> vm_object, AsyncBlockDeviceRequest& request, size_t device_block_size)
+    : m_vm_object(move(vm_object))
 {
     m_dma_region = MM.allocate_kernel_region_with_vmobject(m_vm_object, page_round_up((request.block_count() * device_block_size)), "AHCI Scattered DMA", Region::Access::Read | Region::Access::Write, Region::Cacheable::Yes);
 }
diff --git a/Kernel/VM/ScatterGatherList.h b/Kernel/VM/ScatterGatherList.h
index 0d94cbcfa2..9998d677d4 100644
--- a/Kernel/VM/ScatterGatherList.h
+++ b/Kernel/VM/ScatterGatherList.h
@@ -18,13 +18,13 @@ namespace Kernel {
 
 class ScatterGatherList : public RefCounted<ScatterGatherList> {
 public:
-    static NonnullRefPtr<ScatterGatherList> create(AsyncBlockDeviceRequest&, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size);
+    static RefPtr<ScatterGatherList> create(AsyncBlockDeviceRequest&, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size);
     const VMObject& vmobject() const { return m_vm_object; }
     VirtualAddress dma_region() const { return m_dma_region->vaddr(); }
     size_t scatters_count() const { return m_vm_object->physical_pages().size(); }
 
 private:
-    ScatterGatherList(AsyncBlockDeviceRequest&, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size);
+    ScatterGatherList(NonnullRefPtr<AnonymousVMObject>, AsyncBlockDeviceRequest&, size_t device_block_size);
     NonnullRefPtr<AnonymousVMObject> m_vm_object;
     OwnPtr<Region> m_dma_region;
 };