diff --git a/Kernel/Devices/HID/KeyboardDevice.cpp b/Kernel/Devices/HID/KeyboardDevice.cpp
index 8e0a706d6c..0d8facdd96 100644
--- a/Kernel/Devices/HID/KeyboardDevice.cpp
+++ b/Kernel/Devices/HID/KeyboardDevice.cpp
@@ -289,7 +289,7 @@ KResultOr<size_t> KeyboardDevice::read(FileDescription&, u64, UserOrKernelBuffer
         if (m_queue.is_empty())
             break;
         // Don't return partial data frames.
-        if ((size - nread) < (ssize_t)sizeof(Event))
+        if (size - nread < sizeof(Event))
             break;
         auto event = m_queue.dequeue();
 
diff --git a/Kernel/FileSystem/DevFS.cpp b/Kernel/FileSystem/DevFS.cpp
index 9092656d07..ec80bbe59a 100644
--- a/Kernel/FileSystem/DevFS.cpp
+++ b/Kernel/FileSystem/DevFS.cpp
@@ -81,7 +81,7 @@ DevFSInode::DevFSInode(DevFS& fs)
 {
 }
 
-KResultOr<ssize_t> DevFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
+KResultOr<size_t> DevFSInode::read_bytes(off_t, size_t, UserOrKernelBuffer&, FileDescription*) const
 {
     VERIFY_NOT_REACHED();
 }
@@ -100,7 +100,7 @@ void DevFSInode::flush_metadata()
 {
 }
 
-KResultOr<ssize_t> DevFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
+KResultOr<size_t> DevFSInode::write_bytes(off_t, size_t, const UserOrKernelBuffer&, FileDescription*)
 {
     VERIFY_NOT_REACHED();
 }
@@ -152,7 +152,7 @@ DevFSLinkInode::DevFSLinkInode(DevFS& fs, String name)
     , m_name(name)
 {
 }
-KResultOr<ssize_t> DevFSLinkInode::read_bytes(off_t offset, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const
+KResultOr<size_t> DevFSLinkInode::read_bytes(off_t offset, size_t, UserOrKernelBuffer& buffer, FileDescription*) const
 {
     Locker locker(m_lock);
     VERIFY(offset == 0);
@@ -173,7 +173,7 @@ InodeMetadata DevFSLinkInode::metadata() const
     metadata.mtime = mepoch;
     return metadata;
 }
-KResultOr<ssize_t> DevFSLinkInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& buffer, FileDescription*)
+KResultOr<size_t> DevFSLinkInode::write_bytes(off_t offset, size_t count, const UserOrKernelBuffer& buffer, FileDescription*)
 {
     Locker locker(m_lock);
     VERIFY(offset == 0);
@@ -350,7 +350,7 @@ String DevFSDeviceInode::name() const
     return m_cached_name;
 }
 
-KResultOr<ssize_t> DevFSDeviceInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
+KResultOr<size_t> DevFSDeviceInode::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
 {
     Locker locker(m_lock);
     VERIFY(!!description);
@@ -376,7 +376,7 @@ InodeMetadata DevFSDeviceInode::metadata() const
     metadata.minor_device = m_attached_device->minor();
     return metadata;
 }
-KResultOr<ssize_t> DevFSDeviceInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& buffer, FileDescription* description)
+KResultOr<size_t> DevFSDeviceInode::write_bytes(off_t offset, size_t count, const UserOrKernelBuffer& buffer, FileDescription* description)
 {
     Locker locker(m_lock);
     VERIFY(!!description);
diff --git a/Kernel/FileSystem/DevFS.h b/Kernel/FileSystem/DevFS.h
index 02cf5abe37..d2f175eb05 100644
--- a/Kernel/FileSystem/DevFS.h
+++ b/Kernel/FileSystem/DevFS.h
@@ -57,11 +57,11 @@ public:
 
 protected:
     DevFSInode(DevFS&);
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
@@ -83,9 +83,9 @@ private:
     String determine_name() const;
     DevFSDeviceInode(DevFS&, const Device&);
     // ^Inode
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResult chown(uid_t, gid_t) override;
 
     NonnullRefPtr<Device> m_attached_device;
@@ -106,9 +106,9 @@ public:
 protected:
     DevFSLinkInode(DevFS&, String);
     // ^Inode
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
 
     const String m_name;
     String m_link;
diff --git a/Kernel/FileSystem/DevPtsFS.cpp b/Kernel/FileSystem/DevPtsFS.cpp
index 7d5204b880..b7d9b0a6f1 100644
--- a/Kernel/FileSystem/DevPtsFS.cpp
+++ b/Kernel/FileSystem/DevPtsFS.cpp
@@ -100,12 +100,12 @@ DevPtsFSInode::~DevPtsFSInode()
 {
 }
 
-KResultOr<ssize_t> DevPtsFSInode::read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const
+KResultOr<size_t> DevPtsFSInode::read_bytes(off_t, size_t, UserOrKernelBuffer&, FileDescription*) const
 {
     VERIFY_NOT_REACHED();
 }
 
-KResultOr<ssize_t> DevPtsFSInode::write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*)
+KResultOr<size_t> DevPtsFSInode::write_bytes(off_t, size_t, const UserOrKernelBuffer&, FileDescription*)
 {
     VERIFY_NOT_REACHED();
 }
diff --git a/Kernel/FileSystem/DevPtsFS.h b/Kernel/FileSystem/DevPtsFS.h
index 891bbf2ea2..91437514fd 100644
--- a/Kernel/FileSystem/DevPtsFS.h
+++ b/Kernel/FileSystem/DevPtsFS.h
@@ -47,12 +47,12 @@ private:
     DevPtsFSInode(DevPtsFS&, InodeIndex, SlavePTY*);
 
     // ^Inode
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
diff --git a/Kernel/FileSystem/Ext2FileSystem.cpp b/Kernel/FileSystem/Ext2FileSystem.cpp
index 6ef1eebe37..7b1977ba77 100644
--- a/Kernel/FileSystem/Ext2FileSystem.cpp
+++ b/Kernel/FileSystem/Ext2FileSystem.cpp
@@ -21,7 +21,7 @@
 namespace Kernel {
 
 static constexpr size_t max_block_size = 4096;
-static constexpr ssize_t max_inline_symlink_length = 60;
+static constexpr size_t max_inline_symlink_length = 60;
 
 struct Ext2FSDirectoryEntry {
     String name;
@@ -823,7 +823,7 @@ RefPtr<Inode> Ext2FS::get_inode(InodeIdentifier inode) const
     return new_inode;
 }
 
-KResultOr<ssize_t> Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
+KResultOr<size_t> Ext2FSInode::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
 {
     Locker inode_locker(m_lock);
     VERIFY(offset >= 0);
@@ -837,7 +837,7 @@ KResultOr<ssize_t> Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKe
     // This avoids wasting an entire block on short links. (Most links are short.)
     if (is_symlink() && size() < max_inline_symlink_length) {
         VERIFY(offset == 0);
-        ssize_t nread = min((off_t)size() - offset, static_cast<off_t>(count));
+        size_t nread = min((off_t)size() - offset, static_cast<off_t>(count));
         if (!buffer.write(((const u8*)m_raw_inode.i_block) + offset, (size_t)nread))
             return EFAULT;
         return nread;
@@ -862,7 +862,7 @@ KResultOr<ssize_t> Ext2FSInode::read_bytes(off_t offset, ssize_t count, UserOrKe
 
     int offset_into_first_block = offset % block_size;
 
-    ssize_t nread = 0;
+    size_t nread = 0;
     auto remaining_count = min((off_t)count, (off_t)size() - offset);
 
     dbgln_if(EXT2_VERY_DEBUG, "Ext2FSInode[{}]::read_bytes(): Reading up to {} bytes, {} bytes into inode to {}", identifier(), count, offset, buffer.user_or_kernel_ptr());
@@ -968,10 +968,9 @@ KResult Ext2FSInode::resize(u64 new_size)
     return KSuccess;
 }
 
-KResultOr<ssize_t> Ext2FSInode::write_bytes(off_t offset, ssize_t count, const UserOrKernelBuffer& data, FileDescription* description)
+KResultOr<size_t> Ext2FSInode::write_bytes(off_t offset, size_t count, const UserOrKernelBuffer& data, FileDescription* description)
 {
     VERIFY(offset >= 0);
-    VERIFY(count >= 0);
 
     if (count == 0)
         return 0;
@@ -1017,7 +1016,7 @@ KResultOr<ssize_t> Ext2FSInode::write_bytes(off_t offset, ssize_t count, const U
 
     size_t offset_into_first_block = offset % block_size;
 
-    ssize_t nwritten = 0;
+    size_t nwritten = 0;
     auto remaining_count = min((off_t)count, (off_t)new_size - offset);
 
     dbgln_if(EXT2_VERY_DEBUG, "Ext2FSInode[{}]::write_bytes(): Writing {} bytes, {} bytes into inode from {}", identifier(), count, offset, data.user_or_kernel_ptr());
diff --git a/Kernel/FileSystem/Ext2FileSystem.h b/Kernel/FileSystem/Ext2FileSystem.h
index 6027e28a12..738b506e30 100644
--- a/Kernel/FileSystem/Ext2FileSystem.h
+++ b/Kernel/FileSystem/Ext2FileSystem.h
@@ -38,12 +38,12 @@ public:
 
 private:
     // ^Inode
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& data, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode& child, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
diff --git a/Kernel/FileSystem/FileDescription.cpp b/Kernel/FileSystem/FileDescription.cpp
index 565b19d54a..76e1a3cd62 100644
--- a/Kernel/FileSystem/FileDescription.cpp
+++ b/Kernel/FileSystem/FileDescription.cpp
@@ -203,7 +203,7 @@ KResultOr<NonnullOwnPtr<KBuffer>> FileDescription::read_entire_file()
     return m_inode->read_entire(this);
 }
 
-KResultOr<ssize_t> FileDescription::get_dir_entries(UserOrKernelBuffer& output_buffer, ssize_t size)
+KResultOr<size_t> FileDescription::get_dir_entries(UserOrKernelBuffer& output_buffer, size_t size)
 {
     Locker locker(m_lock, Lock::Mode::Shared);
     if (!is_directory())
@@ -213,9 +213,6 @@ KResultOr<ssize_t> FileDescription::get_dir_entries(UserOrKernelBuffer& output_b
     if (!metadata.is_valid())
         return EIO;
 
-    if (size < 0)
-        return EINVAL;
-
     size_t remaining = size;
     KResult error = KSuccess;
     u8 stack_buffer[PAGE_SIZE];
diff --git a/Kernel/FileSystem/FileDescription.h b/Kernel/FileSystem/FileDescription.h
index 8be270218d..20c678dfaf 100644
--- a/Kernel/FileSystem/FileDescription.h
+++ b/Kernel/FileSystem/FileDescription.h
@@ -56,7 +56,7 @@ public:
     bool can_read() const;
     bool can_write() const;
 
-    KResultOr<ssize_t> get_dir_entries(UserOrKernelBuffer& buffer, ssize_t);
+    KResultOr<size_t> get_dir_entries(UserOrKernelBuffer& buffer, size_t);
 
     KResultOr<NonnullOwnPtr<KBuffer>> read_entire_file();
 
diff --git a/Kernel/FileSystem/Inode.cpp b/Kernel/FileSystem/Inode.cpp
index a5f058f069..f7283fa5b8 100644
--- a/Kernel/FileSystem/Inode.cpp
+++ b/Kernel/FileSystem/Inode.cpp
@@ -51,7 +51,7 @@ KResultOr<NonnullOwnPtr<KBuffer>> Inode::read_entire(FileDescription* descriptio
 {
     KBufferBuilder builder;
 
-    ssize_t nread;
+    size_t nread;
     u8 buffer[4096];
     off_t offset = 0;
     for (;;) {
@@ -60,18 +60,14 @@ KResultOr<NonnullOwnPtr<KBuffer>> Inode::read_entire(FileDescription* descriptio
         if (result.is_error())
             return result.error();
         nread = result.value();
-        VERIFY(nread <= (ssize_t)sizeof(buffer));
+        VERIFY(nread <= sizeof(buffer));
         if (nread <= 0)
             break;
         builder.append((const char*)buffer, nread);
         offset += nread;
-        if (nread < (ssize_t)sizeof(buffer))
+        if (nread < sizeof(buffer))
             break;
     }
-    if (nread < 0) {
-        dmesgln("Inode::read_entire: Error: {}", nread);
-        return KResult((ErrnoCode)-nread);
-    }
 
     auto entire_file = builder.build();
     if (!entire_file)
diff --git a/Kernel/FileSystem/Inode.h b/Kernel/FileSystem/Inode.h
index ed96e9be9e..46e44aefae 100644
--- a/Kernel/FileSystem/Inode.h
+++ b/Kernel/FileSystem/Inode.h
@@ -52,10 +52,10 @@ public:
     virtual KResult attach(FileDescription&) { return KSuccess; }
     virtual void detach(FileDescription&) { }
     virtual void did_seek(FileDescription&, off_t) { }
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const = 0;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const = 0;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const = 0;
     virtual RefPtr<Inode> lookup(StringView name) = 0;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) = 0;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& data, FileDescription*) = 0;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) = 0;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) = 0;
     virtual KResult remove_child(const StringView& name) = 0;
diff --git a/Kernel/FileSystem/Plan9FileSystem.cpp b/Kernel/FileSystem/Plan9FileSystem.cpp
index 56bae74845..aa8bb7df95 100644
--- a/Kernel/FileSystem/Plan9FileSystem.cpp
+++ b/Kernel/FileSystem/Plan9FileSystem.cpp
@@ -171,7 +171,7 @@ public:
 
     const KBuffer& build();
 
-    static constexpr ssize_t max_header_size = 24;
+    static constexpr size_t max_header_size = 24;
 
 private:
     template<typename N>
@@ -634,9 +634,9 @@ KResult Plan9FS::post_message_and_wait_for_a_reply(Message& message)
     }
 }
 
-ssize_t Plan9FS::adjust_buffer_size(ssize_t size) const
+size_t Plan9FS::adjust_buffer_size(size_t size) const
 {
-    ssize_t max_size = m_max_message_size - Message::max_header_size;
+    size_t max_size = m_max_message_size - Message::max_header_size;
     return min(size, max_size);
 }
 
@@ -728,7 +728,7 @@ KResult Plan9FSInode::ensure_open_for_mode(int mode)
     }
 }
 
-KResultOr<ssize_t> Plan9FSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& buffer, FileDescription*) const
+KResultOr<size_t> Plan9FSInode::read_bytes(off_t offset, size_t size, UserOrKernelBuffer& buffer, FileDescription*) const
 {
     auto result = const_cast<Plan9FSInode&>(*this).ensure_open_for_mode(O_RDONLY);
     if (result.is_error())
@@ -767,7 +767,7 @@ KResultOr<ssize_t> Plan9FSInode::read_bytes(off_t offset, ssize_t size, UserOrKe
     return nread;
 }
 
-KResultOr<ssize_t> Plan9FSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& data, FileDescription*)
+KResultOr<size_t> Plan9FSInode::write_bytes(off_t offset, size_t size, const UserOrKernelBuffer& data, FileDescription*)
 {
     auto result = ensure_open_for_mode(O_WRONLY);
     if (result.is_error())
diff --git a/Kernel/FileSystem/Plan9FileSystem.h b/Kernel/FileSystem/Plan9FileSystem.h
index dd654e668b..3a388d451d 100644
--- a/Kernel/FileSystem/Plan9FileSystem.h
+++ b/Kernel/FileSystem/Plan9FileSystem.h
@@ -123,7 +123,7 @@ private:
     KResult post_message_and_explicitly_ignore_reply(Message&);
 
     ProtocolVersion parse_protocol_version(const StringView&) const;
-    ssize_t adjust_buffer_size(ssize_t size) const;
+    size_t adjust_buffer_size(size_t size) const;
 
     void thread_main();
     void ensure_thread();
@@ -156,8 +156,8 @@ public:
     // ^Inode
     virtual InodeMetadata metadata() const override;
     virtual void flush_metadata() override;
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& data, FileDescription*) override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& data, FileDescription*) override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
diff --git a/Kernel/FileSystem/ProcFS.cpp b/Kernel/FileSystem/ProcFS.cpp
index 10adb72459..977162e6bc 100644
--- a/Kernel/FileSystem/ProcFS.cpp
+++ b/Kernel/FileSystem/ProcFS.cpp
@@ -895,7 +895,7 @@ static bool read_sys_bool(InodeIdentifier inode_id, KBufferBuilder& builder)
     return true;
 }
 
-static ssize_t write_sys_bool(InodeIdentifier inode_id, const UserOrKernelBuffer& buffer, size_t size)
+static KResultOr<size_t> write_sys_bool(InodeIdentifier inode_id, const UserOrKernelBuffer& buffer, size_t size)
 {
     auto& variable = SysVariable::for_inode(inode_id);
     VERIFY(variable.type == SysVariable::Type::Boolean);
@@ -913,7 +913,7 @@ static ssize_t write_sys_bool(InodeIdentifier inode_id, const UserOrKernelBuffer
         return result.error();
     VERIFY(result.value() == 0 || (result.value() == 1 && did_read));
     if (result.value() == 0 || !(value == '0' || value == '1'))
-        return (ssize_t)size;
+        return size;
 
     auto* lockable_bool = reinterpret_cast<Lockable<bool>*>(variable.address);
     {
@@ -921,7 +921,7 @@ static ssize_t write_sys_bool(InodeIdentifier inode_id, const UserOrKernelBuffer
         lockable_bool->resource() = value == '1';
     }
     variable.notify();
-    return (ssize_t)size;
+    return size;
 }
 
 static bool read_sys_string(InodeIdentifier inode_id, KBufferBuilder& builder)
@@ -935,14 +935,14 @@ static bool read_sys_string(InodeIdentifier inode_id, KBufferBuilder& builder)
     return true;
 }
 
-static ssize_t write_sys_string(InodeIdentifier inode_id, const UserOrKernelBuffer& buffer, size_t size)
+static KResultOr<size_t> write_sys_string(InodeIdentifier inode_id, const UserOrKernelBuffer& buffer, size_t size)
 {
     auto& variable = SysVariable::for_inode(inode_id);
     VERIFY(variable.type == SysVariable::Type::String);
 
     auto string_copy = buffer.copy_into_string(size);
     if (string_copy.is_null())
-        return -EFAULT;
+        return EFAULT;
 
     {
         auto* lockable_string = reinterpret_cast<Lockable<String>*>(variable.address);
@@ -950,7 +950,7 @@ static ssize_t write_sys_string(InodeIdentifier inode_id, const UserOrKernelBuff
         lockable_string->resource() = move(string_copy);
     }
     variable.notify();
-    return (ssize_t)size;
+    return size;
 }
 
 void ProcFS::add_sys_bool(String&& name, Lockable<bool>& var, Function<void()>&& notify_callback)
@@ -1223,7 +1223,7 @@ InodeMetadata ProcFSInode::metadata() const
     return metadata;
 }
 
-KResultOr<ssize_t> ProcFSInode::read_bytes(off_t offset, ssize_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
+KResultOr<size_t> ProcFSInode::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
 {
     dbgln_if(PROCFS_DEBUG, "ProcFS: read_bytes offset: {} count: {}", offset, count);
     VERIFY(offset >= 0);
@@ -1242,7 +1242,7 @@ KResultOr<ssize_t> ProcFSInode::read_bytes(off_t offset, ssize_t count, UserOrKe
     if (!data_buffer || (size_t)offset >= data_buffer->size())
         return 0;
 
-    ssize_t nread = min(static_cast<off_t>(data_buffer->size() - offset), static_cast<off_t>(count));
+    size_t nread = min(static_cast<off_t>(data_buffer->size() - offset), static_cast<off_t>(count));
     if (!buffer.write(data_buffer->data() + offset, nread))
         return EFAULT;
 
@@ -1454,7 +1454,7 @@ void ProcFSInode::flush_metadata()
 {
 }
 
-KResultOr<ssize_t> ProcFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& buffer, FileDescription*)
+KResultOr<size_t> ProcFSInode::write_bytes(off_t offset, size_t size, const UserOrKernelBuffer& buffer, FileDescription*)
 {
     // For process-specific inodes, hold the process's ptrace lock across the write
     // and refuse to write at all data if the process is not dumpable.
@@ -1478,7 +1478,7 @@ KResultOr<ssize_t> ProcFSInode::write_bytes(off_t offset, ssize_t size, const Us
 
     auto* directory_entry = fs().get_directory_entry(identifier());
 
-    ssize_t (*write_callback)(InodeIdentifier, const UserOrKernelBuffer&, size_t) = nullptr;
+    KResultOr<size_t> (*write_callback)(InodeIdentifier, const UserOrKernelBuffer&, size_t) = nullptr;
 
     if (directory_entry == nullptr) {
         if (to_proc_parent_directory(identifier()) == PDI_Root_sys) {
@@ -1503,10 +1503,10 @@ KResultOr<ssize_t> ProcFSInode::write_bytes(off_t offset, ssize_t size, const Us
     VERIFY(is_persistent_inode(identifier()));
     // FIXME: Being able to write into ProcFS at a non-zero offset seems like something we should maybe support..
     VERIFY(offset == 0);
-    ssize_t nwritten = write_callback(identifier(), buffer, (size_t)size);
-    if (nwritten < 0)
-        dbgln("ProcFS: Writing {} bytes failed: {}", size, nwritten);
-    return nwritten;
+    auto nwritten_or_error = write_callback(identifier(), buffer, (size_t)size);
+    if (nwritten_or_error.is_error())
+        dbgln("ProcFS: Writing {} bytes failed: {}", size, nwritten_or_error.error());
+    return nwritten_or_error;
 }
 
 KResultOr<NonnullRefPtr<Custody>> ProcFSInode::resolve_as_link(Custody& base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level) const
diff --git a/Kernel/FileSystem/ProcFS.h b/Kernel/FileSystem/ProcFS.h
index 4c34709811..a93b8c5414 100644
--- a/Kernel/FileSystem/ProcFS.h
+++ b/Kernel/FileSystem/ProcFS.h
@@ -38,7 +38,7 @@ private:
 
     struct ProcFSDirectoryEntry {
         ProcFSDirectoryEntry() = default;
-        ProcFSDirectoryEntry(const char* a_name, unsigned a_proc_file_type, bool a_supervisor_only, bool (*read_callback)(InodeIdentifier, KBufferBuilder&) = nullptr, ssize_t (*write_callback)(InodeIdentifier, const UserOrKernelBuffer&, size_t) = nullptr, RefPtr<ProcFSInode>&& a_inode = nullptr)
+        ProcFSDirectoryEntry(const char* a_name, unsigned a_proc_file_type, bool a_supervisor_only, bool (*read_callback)(InodeIdentifier, KBufferBuilder&) = nullptr, KResultOr<size_t> (*write_callback)(InodeIdentifier, const UserOrKernelBuffer&, size_t) = nullptr, RefPtr<ProcFSInode>&& a_inode = nullptr)
             : name(a_name)
             , proc_file_type(a_proc_file_type)
             , supervisor_only(a_supervisor_only)
@@ -52,7 +52,7 @@ private:
         unsigned proc_file_type { 0 };
         bool supervisor_only { false };
         bool (*read_callback)(InodeIdentifier, KBufferBuilder&);
-        ssize_t (*write_callback)(InodeIdentifier, const UserOrKernelBuffer&, size_t);
+        KResultOr<size_t> (*write_callback)(InodeIdentifier, const UserOrKernelBuffer&, size_t);
         RefPtr<ProcFSInode> inode;
         InodeIdentifier identifier(unsigned fsid) const;
     };
@@ -77,12 +77,12 @@ private:
     // ^Inode
     virtual KResult attach(FileDescription&) override;
     virtual void did_seek(FileDescription&, off_t) override;
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
@@ -111,12 +111,12 @@ private:
     // ^Inode
     virtual KResult attach(FileDescription&) override;
     virtual void did_seek(FileDescription&, off_t) override;
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const override { VERIFY_NOT_REACHED(); }
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer&, FileDescription*) const override { VERIFY_NOT_REACHED(); }
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override { VERIFY_NOT_REACHED(); }
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override {};
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*) override { VERIFY_NOT_REACHED(); }
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer&, FileDescription*) override { VERIFY_NOT_REACHED(); }
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
diff --git a/Kernel/FileSystem/TmpFS.cpp b/Kernel/FileSystem/TmpFS.cpp
index 08cfb261bc..64e97005fd 100644
--- a/Kernel/FileSystem/TmpFS.cpp
+++ b/Kernel/FileSystem/TmpFS.cpp
@@ -127,11 +127,10 @@ KResult TmpFSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntry
     return KSuccess;
 }
 
-KResultOr<ssize_t> TmpFSInode::read_bytes(off_t offset, ssize_t size, UserOrKernelBuffer& buffer, FileDescription*) const
+KResultOr<size_t> TmpFSInode::read_bytes(off_t offset, size_t size, UserOrKernelBuffer& buffer, FileDescription*) const
 {
     Locker locker(m_lock, Lock::Mode::Shared);
     VERIFY(!is_directory());
-    VERIFY(size >= 0);
     VERIFY(offset >= 0);
 
     if (!m_content)
@@ -148,7 +147,7 @@ KResultOr<ssize_t> TmpFSInode::read_bytes(off_t offset, ssize_t size, UserOrKern
     return size;
 }
 
-KResultOr<ssize_t> TmpFSInode::write_bytes(off_t offset, ssize_t size, const UserOrKernelBuffer& buffer, FileDescription*)
+KResultOr<size_t> TmpFSInode::write_bytes(off_t offset, size_t size, const UserOrKernelBuffer& buffer, FileDescription*)
 {
     Locker locker(m_lock);
     VERIFY(!is_directory());
diff --git a/Kernel/FileSystem/TmpFS.h b/Kernel/FileSystem/TmpFS.h
index 823a21c33c..ec3431b0be 100644
--- a/Kernel/FileSystem/TmpFS.h
+++ b/Kernel/FileSystem/TmpFS.h
@@ -54,12 +54,12 @@ public:
     const TmpFS& fs() const { return static_cast<const TmpFS&>(Inode::fs()); }
 
     // ^Inode
-    virtual KResultOr<ssize_t> read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
+    virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
     virtual InodeMetadata metadata() const override;
     virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
     virtual RefPtr<Inode> lookup(StringView name) override;
     virtual void flush_metadata() override;
-    virtual KResultOr<ssize_t> write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
+    virtual KResultOr<size_t> write_bytes(off_t, size_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
     virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
     virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
     virtual KResult remove_child(const StringView& name) override;
diff --git a/Kernel/Heap/SlabAllocator.cpp b/Kernel/Heap/SlabAllocator.cpp
index cad5a9f87c..d5980ad2aa 100644
--- a/Kernel/Heap/SlabAllocator.cpp
+++ b/Kernel/Heap/SlabAllocator.cpp
@@ -97,7 +97,7 @@ private:
     };
 
     Atomic<FreeSlab*> m_freelist { nullptr };
-    Atomic<ssize_t, AK::MemoryOrder::memory_order_relaxed> m_num_allocated;
+    Atomic<size_t, AK::MemoryOrder::memory_order_relaxed> m_num_allocated;
     size_t m_slab_count;
     void* m_base { nullptr };
     void* m_end { nullptr };
diff --git a/Kernel/Process.h b/Kernel/Process.h
index 8a5c727aed..cd18698ea9 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -270,7 +270,7 @@ public:
     KResultOr<int> sys$inode_watcher_add_watch(Userspace<const Syscall::SC_inode_watcher_add_watch_params*> user_params);
     KResultOr<int> sys$inode_watcher_remove_watch(int fd, int wd);
     KResultOr<int> sys$dbgputch(u8);
-    KResultOr<size_t> sys$dbgputstr(Userspace<const u8*>, int length);
+    KResultOr<size_t> sys$dbgputstr(Userspace<const u8*>, size_t);
     KResultOr<int> sys$dump_backtrace();
     KResultOr<pid_t> sys$gettid();
     KResultOr<int> sys$donate(pid_t tid);
@@ -290,10 +290,10 @@ public:
     KResultOr<mode_t> sys$umask(mode_t);
     KResultOr<int> sys$open(Userspace<const Syscall::SC_open_params*>);
     KResultOr<int> sys$close(int fd);
-    KResultOr<ssize_t> sys$read(int fd, Userspace<u8*>, ssize_t);
-    KResultOr<ssize_t> sys$readv(int fd, Userspace<const struct iovec*> iov, int iov_count);
-    KResultOr<ssize_t> sys$write(int fd, Userspace<const u8*>, ssize_t);
-    KResultOr<ssize_t> sys$writev(int fd, Userspace<const struct iovec*> iov, int iov_count);
+    KResultOr<size_t> sys$read(int fd, Userspace<u8*>, size_t);
+    KResultOr<size_t> sys$readv(int fd, Userspace<const struct iovec*> iov, int iov_count);
+    KResultOr<size_t> sys$write(int fd, Userspace<const u8*>, size_t);
+    KResultOr<size_t> sys$writev(int fd, Userspace<const struct iovec*> iov, int iov_count);
     KResultOr<int> sys$fstat(int fd, Userspace<stat*>);
     KResultOr<int> sys$stat(Userspace<const Syscall::SC_stat_params*>);
     KResultOr<int> sys$lseek(int fd, Userspace<off_t*>, int whence);
@@ -312,7 +312,7 @@ public:
     KResultOr<int> sys$purge(int mode);
     KResultOr<int> sys$select(Userspace<const Syscall::SC_select_params*>);
     KResultOr<int> sys$poll(Userspace<const Syscall::SC_poll_params*>);
-    KResultOr<ssize_t> sys$get_dir_entries(int fd, Userspace<void*>, ssize_t);
+    KResultOr<size_t> sys$get_dir_entries(int fd, Userspace<void*>, size_t);
     KResultOr<int> sys$getcwd(Userspace<char*>, size_t);
     KResultOr<int> sys$chdir(Userspace<const char*>, size_t);
     KResultOr<int> sys$fchdir(int fd);
@@ -321,8 +321,8 @@ public:
     KResultOr<int> sys$clock_gettime(clockid_t, Userspace<timespec*>);
     KResultOr<int> sys$clock_settime(clockid_t, Userspace<const timespec*>);
     KResultOr<int> sys$clock_nanosleep(Userspace<const Syscall::SC_clock_nanosleep_params*>);
-    KResultOr<int> sys$gethostname(Userspace<char*>, ssize_t);
-    KResultOr<int> sys$sethostname(Userspace<const char*>, ssize_t);
+    KResultOr<int> sys$gethostname(Userspace<char*>, size_t);
+    KResultOr<int> sys$sethostname(Userspace<const char*>, size_t);
     KResultOr<int> sys$uname(Userspace<utsname*>);
     KResultOr<int> sys$readlink(Userspace<const Syscall::SC_readlink_params*>);
     KResultOr<int> sys$ttyname(int fd, Userspace<char*>, size_t);
@@ -333,8 +333,8 @@ public:
     KResultOr<int> sys$sigaction(int signum, Userspace<const sigaction*> act, Userspace<sigaction*> old_act);
     KResultOr<int> sys$sigprocmask(int how, Userspace<const sigset_t*> set, Userspace<sigset_t*> old_set);
     KResultOr<int> sys$sigpending(Userspace<sigset_t*>);
-    KResultOr<int> sys$getgroups(ssize_t, Userspace<gid_t*>);
-    KResultOr<int> sys$setgroups(ssize_t, Userspace<const gid_t*>);
+    KResultOr<int> sys$getgroups(size_t, Userspace<gid_t*>);
+    KResultOr<int> sys$setgroups(size_t, Userspace<const gid_t*>);
     KResultOr<int> sys$pipe(int pipefd[2], int flags);
     KResultOr<int> sys$killpg(pid_t pgrp, int sig);
     KResultOr<int> sys$seteuid(uid_t);
@@ -367,8 +367,8 @@ public:
     KResultOr<int> sys$accept4(Userspace<const Syscall::SC_accept4_params*>);
     KResultOr<int> sys$connect(int sockfd, Userspace<const sockaddr*>, socklen_t);
     KResultOr<int> sys$shutdown(int sockfd, int how);
-    KResultOr<ssize_t> sys$sendmsg(int sockfd, Userspace<const struct msghdr*>, int flags);
-    KResultOr<ssize_t> sys$recvmsg(int sockfd, Userspace<struct msghdr*>, int flags);
+    KResultOr<size_t> sys$sendmsg(int sockfd, Userspace<const struct msghdr*>, int flags);
+    KResultOr<size_t> sys$recvmsg(int sockfd, Userspace<struct msghdr*>, int flags);
     KResultOr<int> sys$getsockopt(Userspace<const Syscall::SC_getsockopt_params*>);
     KResultOr<int> sys$setsockopt(Userspace<const Syscall::SC_setsockopt_params*>);
     KResultOr<int> sys$getsockname(Userspace<const Syscall::SC_getsockname_params*>);
@@ -529,7 +529,7 @@ private:
     void delete_perf_events_buffer();
 
     KResult do_exec(NonnullRefPtr<FileDescription> main_program_description, Vector<String> arguments, Vector<String> environment, RefPtr<FileDescription> interpreter_description, Thread*& new_main_thread, u32& prev_flags, const Elf32_Ehdr& main_program_header);
-    KResultOr<ssize_t> do_write(FileDescription&, const UserOrKernelBuffer&, size_t);
+    KResultOr<size_t> do_write(FileDescription&, const UserOrKernelBuffer&, size_t);
 
     KResultOr<int> do_statvfs(String path, statvfs* buf);
 
diff --git a/Kernel/Storage/StorageDevice.cpp b/Kernel/Storage/StorageDevice.cpp
index 0d904105f5..ab526deb19 100644
--- a/Kernel/Storage/StorageDevice.cpp
+++ b/Kernel/Storage/StorageDevice.cpp
@@ -41,7 +41,7 @@ KResultOr<size_t> StorageDevice::read(FileDescription&, u64 offset, UserOrKernel
 {
     unsigned index = offset / block_size();
     u16 whole_blocks = len / block_size();
-    ssize_t remaining = len % block_size();
+    size_t remaining = len % block_size();
 
     unsigned blocks_per_page = PAGE_SIZE / block_size();
 
@@ -106,7 +106,7 @@ KResultOr<size_t> StorageDevice::write(FileDescription&, u64 offset, const UserO
 {
     unsigned index = offset / block_size();
     u16 whole_blocks = len / block_size();
-    ssize_t remaining = len % block_size();
+    size_t remaining = len % block_size();
 
     unsigned blocks_per_page = PAGE_SIZE / block_size();
 
diff --git a/Kernel/Syscalls/anon_create.cpp b/Kernel/Syscalls/anon_create.cpp
index cb30655806..8f8aa413e1 100644
--- a/Kernel/Syscalls/anon_create.cpp
+++ b/Kernel/Syscalls/anon_create.cpp
@@ -21,6 +21,9 @@ KResultOr<int> Process::sys$anon_create(size_t size, int options)
     if (size % PAGE_SIZE)
         return EINVAL;
 
+    if (size > NumericLimits<ssize_t>::max())
+        return EINVAL;
+
     int new_fd = alloc_fd();
     if (new_fd < 0)
         return new_fd;
diff --git a/Kernel/Syscalls/chdir.cpp b/Kernel/Syscalls/chdir.cpp
index c0aff80211..bded5a93fb 100644
--- a/Kernel/Syscalls/chdir.cpp
+++ b/Kernel/Syscalls/chdir.cpp
@@ -45,6 +45,9 @@ KResultOr<int> Process::sys$getcwd(Userspace<char*> buffer, size_t size)
 {
     REQUIRE_PROMISE(rpath);
 
+    if (size > NumericLimits<ssize_t>::max())
+        return EINVAL;
+
     auto path = current_directory().absolute_path();
 
     size_t ideal_size = path.length() + 1;
diff --git a/Kernel/Syscalls/debug.cpp b/Kernel/Syscalls/debug.cpp
index 7f864e5da2..c3f4872a36 100644
--- a/Kernel/Syscalls/debug.cpp
+++ b/Kernel/Syscalls/debug.cpp
@@ -23,15 +23,18 @@ KResultOr<int> Process::sys$dbgputch(u8 ch)
     return 0;
 }
 
-KResultOr<size_t> Process::sys$dbgputstr(Userspace<const u8*> characters, int length)
+KResultOr<size_t> Process::sys$dbgputstr(Userspace<const u8*> characters, size_t size)
 {
-    if (length <= 0)
+    if (size <= 0)
         return 0;
 
-    auto buffer = UserOrKernelBuffer::for_user_buffer(characters, length);
+    if (size > NumericLimits<ssize_t>::max())
+        return EINVAL;
+
+    auto buffer = UserOrKernelBuffer::for_user_buffer(characters, size);
     if (!buffer.has_value())
         return EFAULT;
-    return buffer.value().read_buffered<1024>(length, [&](u8 const* buffer, size_t buffer_size) {
+    return buffer.value().read_buffered<1024>(size, [&](u8 const* buffer, size_t buffer_size) {
         for (size_t i = 0; i < buffer_size; ++i)
             IO::out8(IO::BOCHS_DEBUG_PORT, buffer[i]);
         return buffer_size;
diff --git a/Kernel/Syscalls/get_dir_entries.cpp b/Kernel/Syscalls/get_dir_entries.cpp
index 8219cfdecc..b449e88dcd 100644
--- a/Kernel/Syscalls/get_dir_entries.cpp
+++ b/Kernel/Syscalls/get_dir_entries.cpp
@@ -9,10 +9,10 @@
 
 namespace Kernel {
 
-KResultOr<ssize_t> Process::sys$get_dir_entries(int fd, Userspace<void*> user_buffer, ssize_t user_size)
+KResultOr<size_t> Process::sys$get_dir_entries(int fd, Userspace<void*> user_buffer, size_t user_size)
 {
     REQUIRE_PROMISE(stdio);
-    if (user_size < 0)
+    if (user_size > NumericLimits<ssize_t>::max())
         return EINVAL;
     auto description = file_description(fd);
     if (!description)
diff --git a/Kernel/Syscalls/getrandom.cpp b/Kernel/Syscalls/getrandom.cpp
index 8000b25ef2..c92cc5778e 100644
--- a/Kernel/Syscalls/getrandom.cpp
+++ b/Kernel/Syscalls/getrandom.cpp
@@ -16,7 +16,7 @@ namespace Kernel {
 KResultOr<size_t> Process::sys$getrandom(Userspace<void*> buffer, size_t buffer_size, [[maybe_unused]] unsigned flags)
 {
     REQUIRE_PROMISE(stdio);
-    if (buffer_size <= 0)
+    if (buffer_size > NumericLimits<ssize_t>::max())
         return EINVAL;
 
     auto data_buffer = UserOrKernelBuffer::for_user_buffer(buffer, buffer_size);
diff --git a/Kernel/Syscalls/getuid.cpp b/Kernel/Syscalls/getuid.cpp
index 48d61d0274..349b0f651d 100644
--- a/Kernel/Syscalls/getuid.cpp
+++ b/Kernel/Syscalls/getuid.cpp
@@ -48,14 +48,12 @@ KResultOr<int> Process::sys$getresgid(Userspace<gid_t*> rgid, Userspace<gid_t*>
     return 0;
 }
 
-KResultOr<int> Process::sys$getgroups(ssize_t count, Userspace<gid_t*> user_gids)
+KResultOr<int> Process::sys$getgroups(size_t count, Userspace<gid_t*> user_gids)
 {
     REQUIRE_PROMISE(stdio);
-    if (count < 0)
-        return EINVAL;
     if (!count)
         return extra_gids().size();
-    if (count != (int)extra_gids().size())
+    if (count != extra_gids().size())
         return EINVAL;
 
     if (!copy_to_user(user_gids, extra_gids().data(), sizeof(gid_t) * count))
diff --git a/Kernel/Syscalls/hostname.cpp b/Kernel/Syscalls/hostname.cpp
index cc3b4b7f48..b5e08f098f 100644
--- a/Kernel/Syscalls/hostname.cpp
+++ b/Kernel/Syscalls/hostname.cpp
@@ -11,10 +11,10 @@ namespace Kernel {
 extern String* g_hostname;
 extern Lock* g_hostname_lock;
 
-KResultOr<int> Process::sys$gethostname(Userspace<char*> buffer, ssize_t size)
+KResultOr<int> Process::sys$gethostname(Userspace<char*> buffer, size_t size)
 {
     REQUIRE_PROMISE(stdio);
-    if (size < 0)
+    if (size > NumericLimits<ssize_t>::max())
         return EINVAL;
     Locker locker(*g_hostname_lock, Lock::Mode::Shared);
     if ((size_t)size < (g_hostname->length() + 1))
@@ -24,13 +24,11 @@ KResultOr<int> Process::sys$gethostname(Userspace<char*> buffer, ssize_t size)
     return 0;
 }
 
-KResultOr<int> Process::sys$sethostname(Userspace<const char*> hostname, ssize_t length)
+KResultOr<int> Process::sys$sethostname(Userspace<const char*> hostname, size_t length)
 {
     REQUIRE_NO_PROMISES;
     if (!is_superuser())
         return EPERM;
-    if (length < 0)
-        return EINVAL;
     Locker locker(*g_hostname_lock, Lock::Mode::Exclusive);
     if (length > 64)
         return ENAMETOOLONG;
diff --git a/Kernel/Syscalls/read.cpp b/Kernel/Syscalls/read.cpp
index 61fb800997..df9c30ab2b 100644
--- a/Kernel/Syscalls/read.cpp
+++ b/Kernel/Syscalls/read.cpp
@@ -12,7 +12,7 @@ namespace Kernel {
 
 using BlockFlags = Thread::FileBlocker::BlockFlags;
 
-KResultOr<ssize_t> Process::sys$readv(int fd, Userspace<const struct iovec*> iov, int iov_count)
+KResultOr<size_t> Process::sys$readv(int fd, Userspace<const struct iovec*> iov, int iov_count)
 {
     REQUIRE_PROMISE(stdio);
     if (iov_count < 0)
@@ -68,13 +68,13 @@ KResultOr<ssize_t> Process::sys$readv(int fd, Userspace<const struct iovec*> iov
     return nread;
 }
 
-KResultOr<ssize_t> Process::sys$read(int fd, Userspace<u8*> buffer, ssize_t size)
+KResultOr<size_t> Process::sys$read(int fd, Userspace<u8*> buffer, size_t size)
 {
     REQUIRE_PROMISE(stdio);
-    if (size < 0)
-        return EINVAL;
     if (size == 0)
         return 0;
+    if (size > NumericLimits<ssize_t>::max())
+        return EINVAL;
     dbgln_if(IO_DEBUG, "sys$read({}, {}, {})", fd, buffer.ptr(), size);
     auto description = file_description(fd);
     if (!description)
diff --git a/Kernel/Syscalls/setuid.cpp b/Kernel/Syscalls/setuid.cpp
index 729a9f2196..0269e71464 100644
--- a/Kernel/Syscalls/setuid.cpp
+++ b/Kernel/Syscalls/setuid.cpp
@@ -148,11 +148,9 @@ KResultOr<int> Process::sys$setresgid(gid_t new_rgid, gid_t new_egid, gid_t new_
     return 0;
 }
 
-KResultOr<int> Process::sys$setgroups(ssize_t count, Userspace<const gid_t*> user_gids)
+KResultOr<int> Process::sys$setgroups(size_t count, Userspace<const gid_t*> user_gids)
 {
     REQUIRE_PROMISE(id);
-    if (count < 0)
-        return EINVAL;
     if (!is_superuser())
         return EPERM;
 
diff --git a/Kernel/Syscalls/socket.cpp b/Kernel/Syscalls/socket.cpp
index 32f6c3e8cf..1c70666a0a 100644
--- a/Kernel/Syscalls/socket.cpp
+++ b/Kernel/Syscalls/socket.cpp
@@ -179,7 +179,7 @@ KResultOr<int> Process::sys$shutdown(int sockfd, int how)
     return socket.shutdown(how);
 }
 
-KResultOr<ssize_t> Process::sys$sendmsg(int sockfd, Userspace<const struct msghdr*> user_msg, int flags)
+KResultOr<size_t> Process::sys$sendmsg(int sockfd, Userspace<const struct msghdr*> user_msg, int flags)
 {
     REQUIRE_PROMISE(stdio);
     struct msghdr msg;
@@ -193,6 +193,8 @@ KResultOr<ssize_t> Process::sys$sendmsg(int sockfd, Userspace<const struct msghd
         return ENOMEM;
     if (!copy_n_from_user(iovs.data(), msg.msg_iov, msg.msg_iovlen))
         return EFAULT;
+    if (iovs[0].iov_len > NumericLimits<ssize_t>::max())
+        return EINVAL;
 
     Userspace<const sockaddr*> user_addr((FlatPtr)msg.msg_name);
     socklen_t addr_length = msg.msg_namelen;
@@ -208,13 +210,10 @@ KResultOr<ssize_t> Process::sys$sendmsg(int sockfd, Userspace<const struct msghd
     auto data_buffer = UserOrKernelBuffer::for_user_buffer((u8*)iovs[0].iov_base, iovs[0].iov_len);
     if (!data_buffer.has_value())
         return EFAULT;
-    auto result = socket.sendto(*description, data_buffer.value(), iovs[0].iov_len, flags, user_addr, addr_length);
-    if (result.is_error())
-        return result.error();
-    return result.value();
+    return socket.sendto(*description, data_buffer.value(), iovs[0].iov_len, flags, user_addr, addr_length);
 }
 
-KResultOr<ssize_t> Process::sys$recvmsg(int sockfd, Userspace<struct msghdr*> user_msg, int flags)
+KResultOr<size_t> Process::sys$recvmsg(int sockfd, Userspace<struct msghdr*> user_msg, int flags)
 {
     REQUIRE_PROMISE(stdio);
 
diff --git a/Kernel/Syscalls/write.cpp b/Kernel/Syscalls/write.cpp
index 0ba686ca48..88c8217321 100644
--- a/Kernel/Syscalls/write.cpp
+++ b/Kernel/Syscalls/write.cpp
@@ -11,7 +11,7 @@
 
 namespace Kernel {
 
-KResultOr<ssize_t> Process::sys$writev(int fd, Userspace<const struct iovec*> iov, int iov_count)
+KResultOr<size_t> Process::sys$writev(int fd, Userspace<const struct iovec*> iov, int iov_count)
 {
     REQUIRE_PROMISE(stdio);
     if (iov_count < 0)
@@ -57,9 +57,9 @@ KResultOr<ssize_t> Process::sys$writev(int fd, Userspace<const struct iovec*> io
     return nwritten;
 }
 
-KResultOr<ssize_t> Process::do_write(FileDescription& description, const UserOrKernelBuffer& data, size_t data_size)
+KResultOr<size_t> Process::do_write(FileDescription& description, const UserOrKernelBuffer& data, size_t data_size)
 {
-    ssize_t total_nwritten = 0;
+    size_t total_nwritten = 0;
 
     if (description.should_append() && description.file().is_seekable()) {
         auto seek_result = description.seek(0, SEEK_END);
@@ -96,13 +96,13 @@ KResultOr<ssize_t> Process::do_write(FileDescription& description, const UserOrK
     return total_nwritten;
 }
 
-KResultOr<ssize_t> Process::sys$write(int fd, Userspace<const u8*> data, ssize_t size)
+KResultOr<size_t> Process::sys$write(int fd, Userspace<const u8*> data, size_t size)
 {
     REQUIRE_PROMISE(stdio);
-    if (size < 0)
-        return EINVAL;
     if (size == 0)
         return 0;
+    if (size > NumericLimits<ssize_t>::max())
+        return EINVAL;
 
     dbgln_if(IO_DEBUG, "sys$write({}, {}, {})", fd, data.ptr(), size);
     auto description = file_description(fd);
diff --git a/Kernel/UserOrKernelBuffer.h b/Kernel/UserOrKernelBuffer.h
index 3407975708..93c023a47b 100644
--- a/Kernel/UserOrKernelBuffer.h
+++ b/Kernel/UserOrKernelBuffer.h
@@ -44,7 +44,7 @@ public:
     [[nodiscard]] bool is_kernel_buffer() const;
     [[nodiscard]] const void* user_or_kernel_ptr() const { return m_buffer; }
 
-    [[nodiscard]] UserOrKernelBuffer offset(ssize_t offset) const
+    [[nodiscard]] UserOrKernelBuffer offset(size_t offset) const
     {
         if (!m_buffer)
             return *this;
@@ -97,9 +97,10 @@ public:
         size_t nwritten = 0;
         while (nwritten < len) {
             auto to_copy = min(sizeof(buffer), len - nwritten);
-            ssize_t copied = f(buffer, to_copy);
-            if (copied < 0)
-                return copied;
+            KResultOr<size_t> copied_or_error = f(buffer, to_copy);
+            if (copied_or_error.is_error())
+                return copied_or_error.error();
+            auto copied = copied_or_error.value();
             VERIFY((size_t)copied <= to_copy);
             if (!write(buffer, nwritten, (size_t)copied))
                 return EFAULT;
diff --git a/Kernel/VM/Region.cpp b/Kernel/VM/Region.cpp
index d7ace9d177..0c3a03ab80 100644
--- a/Kernel/VM/Region.cpp
+++ b/Kernel/VM/Region.cpp
@@ -541,7 +541,7 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region, Scoped
     // Reading the page may block, so release the MM lock temporarily
     mm_lock.unlock();
 
-    KResultOr<ssize_t> result(KSuccess);
+    KResultOr<size_t> result(KSuccess);
     {
         ScopedLockRelease release_paging_lock(vmobject().m_paging_lock);
         auto buffer = UserOrKernelBuffer::for_kernel_buffer(page_buffer);