Kernel: Handle OOM from KBuffer usage in Ext2FS::get_bitmap_block()

Fixes up error handling on an OOM-able path, and removes one more usage
of KBuffer::create_with_size.

2 files changed, 9 insertions, 7 deletions

diff --git a/Kernel/FileSystem/Ext2FileSystem.cpp b/Kernel/FileSystem/Ext2FileSystem.cpp
index c199cfe611..579f5e2f29 100644
--- a/Kernel/FileSystem/Ext2FileSystem.cpp
+++ b/Kernel/FileSystem/Ext2FileSystem.cpp
@@ -701,7 +701,7 @@ void Ext2FS::flush_writes()
         }
         for (auto& cached_bitmap : m_cached_bitmaps) {
             if (cached_bitmap->dirty) {
-                auto buffer = UserOrKernelBuffer::for_kernel_buffer(cached_bitmap->buffer.data());
+                auto buffer = UserOrKernelBuffer::for_kernel_buffer(cached_bitmap->buffer->data());
                 if (auto result = write_block(cached_bitmap->bitmap_block_index, buffer, block_size()); result.is_error()) {
                     dbgln("Ext2FS[{}]::flush_writes(): Failed to write blocks: {}", fsid(), result.error());
                 }
@@ -1499,13 +1499,15 @@ KResultOr<Ext2FS::CachedBitmap*> Ext2FS::get_bitmap_block(BlockIndex bitmap_bloc
             return cached_bitmap;
     }
 
-    auto block = KBuffer::create_with_size(block_size(), Region::Access::Read | Region::Access::Write, "Ext2FS: Cached bitmap block");
-    auto buffer = UserOrKernelBuffer::for_kernel_buffer(block.data());
+    auto block = KBuffer::try_create_with_size(block_size(), Region::Access::Read | Region::Access::Write, "Ext2FS: Cached bitmap block");
+    if (!block)
+        return ENOMEM;
+    auto buffer = UserOrKernelBuffer::for_kernel_buffer(block->data());
     if (auto result = read_block(bitmap_block_index, &buffer, block_size()); result.is_error()) {
         dbgln("Ext2FS: Failed to load bitmap block {}", bitmap_block_index);
         return result;
     }
-    auto new_bitmap = adopt_own_if_nonnull(new (nothrow) CachedBitmap(bitmap_block_index, move(block)));
+    auto new_bitmap = adopt_own_if_nonnull(new (nothrow) CachedBitmap(bitmap_block_index, block.release_nonnull()));
     if (!new_bitmap)
         return ENOMEM;
     if (!m_cached_bitmaps.try_append(move(new_bitmap)))
diff --git a/Kernel/FileSystem/Ext2FileSystem.h b/Kernel/FileSystem/Ext2FileSystem.h
index d3318ab2e4..d3f1161087 100644
--- a/Kernel/FileSystem/Ext2FileSystem.h
+++ b/Kernel/FileSystem/Ext2FileSystem.h
@@ -168,15 +168,15 @@ private:
     bool m_block_group_descriptors_dirty { false };
 
     struct CachedBitmap {
-        CachedBitmap(BlockIndex bi, KBuffer&& buf)
+        CachedBitmap(BlockIndex bi, NonnullOwnPtr<KBuffer> buf)
             : bitmap_block_index(bi)
             , buffer(move(buf))
         {
         }
         BlockIndex bitmap_block_index { 0 };
         bool dirty { false };
-        KBuffer buffer;
-        BitmapView bitmap(u32 blocks_per_group) { return BitmapView { buffer.data(), blocks_per_group }; }
+        NonnullOwnPtr<KBuffer> buffer;
+        BitmapView bitmap(u32 blocks_per_group) { return BitmapView { buffer->data(), blocks_per_group }; }
     };
 
     KResultOr<CachedBitmap*> get_bitmap_block(BlockIndex);