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.

1 files changed, 2 insertions, 0 deletions

diff --git a/Kernel/Devices/SB16.cpp b/Kernel/Devices/SB16.cpp
index fa48d20db8..2ae61c8ad2 100644
--- a/Kernel/Devices/SB16.cpp
+++ b/Kernel/Devices/SB16.cpp
@@ -230,6 +230,8 @@ KResultOr<size_t> SB16::write(FileDescription&, u64, const UserOrKernelBuffer& d
         if (!page)
             return ENOMEM;
         auto vmobject = AnonymousVMObject::create_with_physical_page(*page);
+        if (!vmobject)
+            return ENOMEM;
         m_dma_region = MM.allocate_kernel_region_with_vmobject(*vmobject, PAGE_SIZE, "SB16 DMA buffer", Region::Access::Write);
         if (!m_dma_region)
             return ENOMEM;