diff --git a/Kernel/FileSystem/Inode.cpp b/Kernel/FileSystem/Inode.cpp
index 7d3537d906..5d5b558a27 100644
--- a/Kernel/FileSystem/Inode.cpp
+++ b/Kernel/FileSystem/Inode.cpp
@@ -57,7 +57,7 @@ KResultOr<NonnullOwnPtr<KBuffer>> Inode::read_entire(FileDescription* descriptio
         VERIFY(nread <= sizeof(buffer));
         if (nread == 0)
             break;
-        builder.append((const char*)buffer, nread);
+        TRY(builder.append((const char*)buffer, nread));
         offset += nread;
         if (nread < sizeof(buffer))
             break;
diff --git a/Kernel/FileSystem/Plan9FileSystem.cpp b/Kernel/FileSystem/Plan9FileSystem.cpp
index cb3bbcd727..2532ee1eac 100644
--- a/Kernel/FileSystem/Plan9FileSystem.cpp
+++ b/Kernel/FileSystem/Plan9FileSystem.cpp
@@ -178,7 +178,8 @@ private:
     Message& append_number(N number)
     {
         VERIFY(!m_have_been_built);
-        m_builder.append(reinterpret_cast<const char*>(&number), sizeof(number));
+        // FIXME: Handle append failure.
+        (void)m_builder.append(reinterpret_cast<const char*>(&number), sizeof(number));
         return *this;
     }
 
@@ -264,14 +265,16 @@ Plan9FS::Message& Plan9FS::Message::operator<<(u64 number)
 Plan9FS::Message& Plan9FS::Message::operator<<(const StringView& string)
 {
     *this << static_cast<u16>(string.length());
-    m_builder.append(string);
+    // FIXME: Handle append failure.
+    (void)m_builder.append(string);
     return *this;
 }
 
 void Plan9FS::Message::append_data(const StringView& data)
 {
     *this << static_cast<u32>(data.length());
-    m_builder.append(data);
+    // FIXME: Handle append failure.
+    (void)m_builder.append(data);
 }
 
 Plan9FS::Message::Decoder& Plan9FS::Message::Decoder::operator>>(u8& number)
diff --git a/Kernel/GlobalProcessExposed.cpp b/Kernel/GlobalProcessExposed.cpp
index 8b9ebc267d..1725632f06 100644
--- a/Kernel/GlobalProcessExposed.cpp
+++ b/Kernel/GlobalProcessExposed.cpp
@@ -336,7 +336,8 @@ private:
     ProcFSSelfProcessDirectory();
     virtual bool acquire_link(KBufferBuilder& builder) override
     {
-        builder.appendff("{}", Process::current().pid().value());
+        if (builder.appendff("{}", Process::current().pid().value()).is_error())
+            return false;
         return true;
     }
 };
@@ -559,8 +560,10 @@ private:
     virtual bool output(KBufferBuilder& builder) override
     {
         InterruptDisabler disabler;
-        for (char ch : ConsoleDevice::the().logbuffer())
-            builder.append(ch);
+        for (char ch : ConsoleDevice::the().logbuffer()) {
+            if (builder.append(ch).is_error())
+                return false;
+        }
         return true;
     }
 };
@@ -664,7 +667,8 @@ private:
     ProcFSUptime();
     virtual bool output(KBufferBuilder& builder) override
     {
-        builder.appendff("{}\n", TimeManagement::the().uptime_ms() / 1000);
+        if (builder.appendff("{}\n", TimeManagement::the().uptime_ms() / 1000).is_error())
+            return false;
         return true;
     }
 };
@@ -676,8 +680,10 @@ private:
     ProcFSCommandLine();
     virtual bool output(KBufferBuilder& builder) override
     {
-        builder.append(kernel_command_line().string());
-        builder.append('\n');
+        if (builder.append(kernel_command_line().string()).is_error())
+            return false;
+        if (builder.append('\n').is_error())
+            return false;
         return true;
     }
 };
@@ -739,7 +745,8 @@ private:
     {
         if (!Process::current().is_superuser())
             return false;
-        builder.append(String::number(kernel_load_base));
+        if (builder.append(String::number(kernel_load_base)).is_error())
+            return false;
         return true;
     }
 };
diff --git a/Kernel/KBufferBuilder.cpp b/Kernel/KBufferBuilder.cpp
index 04eb90b58d..9ce17b762c 100644
--- a/Kernel/KBufferBuilder.cpp
+++ b/Kernel/KBufferBuilder.cpp
@@ -45,68 +45,73 @@ KBufferBuilder::KBufferBuilder()
 {
 }
 
-void KBufferBuilder::append_bytes(ReadonlyBytes bytes)
+KResult KBufferBuilder::append_bytes(ReadonlyBytes bytes)
 {
     if (!check_expand(bytes.size()))
-        return;
+        return ENOMEM;
     memcpy(insertion_ptr(), bytes.data(), bytes.size());
     m_size += bytes.size();
+    return KSuccess;
 }
 
-void KBufferBuilder::append(const StringView& str)
+KResult KBufferBuilder::append(const StringView& str)
 {
     if (str.is_empty())
-        return;
+        return KSuccess;
     if (!check_expand(str.length()))
-        return;
+        return ENOMEM;
     memcpy(insertion_ptr(), str.characters_without_null_termination(), str.length());
     m_size += str.length();
+    return KSuccess;
 }
 
-void KBufferBuilder::append(const char* characters, int length)
+KResult KBufferBuilder::append(const char* characters, int length)
 {
     if (!length)
-        return;
+        return KSuccess;
     if (!check_expand(length))
-        return;
+        return ENOMEM;
     memcpy(insertion_ptr(), characters, length);
     m_size += length;
+    return KSuccess;
 }
 
-void KBufferBuilder::append(char ch)
+KResult KBufferBuilder::append(char ch)
 {
     if (!check_expand(1))
-        return;
+        return ENOMEM;
     insertion_ptr()[0] = ch;
     m_size += 1;
+    return KSuccess;
 }
 
-void KBufferBuilder::append_escaped_for_json(const StringView& string)
+KResult KBufferBuilder::append_escaped_for_json(const StringView& string)
 {
     for (auto ch : string) {
         switch (ch) {
         case '\e':
-            append("\\u001B");
+            TRY(append("\\u001B"));
             break;
         case '\b':
-            append("\\b");
+            TRY(append("\\b"));
             break;
         case '\n':
-            append("\\n");
+            TRY(append("\\n"));
             break;
         case '\t':
-            append("\\t");
+            TRY(append("\\t"));
             break;
         case '\"':
-            append("\\\"");
+            TRY(append("\\\""));
             break;
         case '\\':
-            append("\\\\");
+            TRY(append("\\\\"));
             break;
         default:
-            append(ch);
+            TRY(append(ch));
         }
     }
+    return KSuccess;
 }
 
 }
diff --git a/Kernel/KBufferBuilder.h b/Kernel/KBufferBuilder.h
index 728e83d79c..fc86806c80 100644
--- a/Kernel/KBufferBuilder.h
+++ b/Kernel/KBufferBuilder.h
@@ -20,26 +20,33 @@ public:
     KBufferBuilder(KBufferBuilder&&) = default;
     ~KBufferBuilder() = default;
 
-    void append(const StringView&);
-    void append(char);
-    void append(const char*, int);
+    KResult append(const StringView&);
+    KResult append(char);
+    KResult append(const char*, int);
 
-    void append_escaped_for_json(const StringView&);
-    void append_bytes(ReadonlyBytes);
+    KResult append_escaped_for_json(const StringView&);
+    KResult append_bytes(ReadonlyBytes);
 
     template<typename... Parameters>
-    void appendff(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters)
+    KResult appendff(CheckedFormatString<Parameters...>&& fmtstr, const Parameters&... parameters)
     {
         // FIXME: This really not ideal, but vformat expects StringBuilder.
         StringBuilder builder;
         AK::VariadicFormatParams variadic_format_params { parameters... };
         vformat(builder, fmtstr.view(), variadic_format_params);
-        append_bytes(builder.string_view().bytes());
+        return append_bytes(builder.string_view().bytes());
     }
 
     bool flush();
     OwnPtr<KBuffer> build();
 
+    ReadonlyBytes bytes() const
+    {
+        if (!m_buffer)
+            return {};
+        return ReadonlyBytes { m_buffer->data(), m_buffer->size() };
+    }
+
 private:
     bool check_expand(size_t);
     u8* insertion_ptr()
diff --git a/Kernel/ProcessExposed.h b/Kernel/ProcessExposed.h
index 757c094b4e..edc2c7d428 100644
--- a/Kernel/ProcessExposed.h
+++ b/Kernel/ProcessExposed.h
@@ -184,7 +184,8 @@ protected:
     }
     virtual bool output(KBufferBuilder& builder) override
     {
-        builder.appendff("{}\n", value());
+        if (builder.appendff("{}\n", value()).is_error())
+            return false;
         return true;
     }
 };
diff --git a/Kernel/ProcessSpecificExposed.cpp b/Kernel/ProcessSpecificExposed.cpp
index 4906725fd4..b2b670762f 100644
--- a/Kernel/ProcessSpecificExposed.cpp
+++ b/Kernel/ProcessSpecificExposed.cpp
@@ -81,7 +81,7 @@ KResultOr<size_t> Process::procfs_get_file_description_link(unsigned fd, KBuffer
 {
     auto file_description = TRY(m_fds.file_description(fd));
     auto data = file_description->absolute_path();
-    builder.append(data);
+    TRY(builder.append(data));
     return data.length();
 }
 
@@ -249,8 +249,7 @@ KResult Process::procfs_get_virtual_memory_stats(KBufferBuilder& builder) const
 
 KResult Process::procfs_get_current_work_directory_link(KBufferBuilder& builder) const
 {
-    builder.append_bytes(const_cast<Process&>(*this).current_directory().absolute_path().bytes());
-    return KSuccess;
+    return builder.append_bytes(const_cast<Process&>(*this).current_directory().absolute_path().bytes());
 }
 
 mode_t Process::binary_link_required_mode() const
@@ -265,8 +264,7 @@ KResult Process::procfs_get_binary_link(KBufferBuilder& builder) const
     auto* custody = executable();
     if (!custody)
         return KResult(ENOEXEC);
-    builder.append(custody->absolute_path().bytes());
-    return KSuccess;
+    return builder.append(custody->absolute_path().bytes());
 }
 
 }