From 0f6f86338294899fcd0e8cd9961fafbf604fa197 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sat, 14 Aug 2021 23:00:06 +0200
Subject: [PATCH] Kernel: Convert remaining users of copy_string_from_user()

This patch replaces the remaining users of this API with the new
try_copy_kstring_from_user() instead. Note that we still convert to a
String for continued processing, and I've added FIXME about continuing
work on using KString all the way.
---
 Kernel/Syscalls/execve.cpp   |  8 ++++++--
 Kernel/Syscalls/hostname.cpp |  9 +++++----
 Kernel/Syscalls/module.cpp   |  8 ++++----
 Kernel/Syscalls/process.cpp  | 11 ++++++-----
 4 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/Kernel/Syscalls/execve.cpp b/Kernel/Syscalls/execve.cpp
index eef9d081de..a9ff468620 100644
--- a/Kernel/Syscalls/execve.cpp
+++ b/Kernel/Syscalls/execve.cpp
@@ -970,9 +970,13 @@ KResultOr<FlatPtr> Process::sys$execve(Userspace<const Syscall::SC_execve_params
         if (!copy_from_user(strings.data(), list.strings, size.value()))
             return false;
         for (size_t i = 0; i < list.length; ++i) {
-            auto string = copy_string_from_user(strings[i]);
-            if (string.is_null())
+            auto string_or_error = try_copy_kstring_from_user(strings[i]);
+            if (string_or_error.is_error()) {
+                // FIXME: Propagate the error.
                 return false;
+            }
+            // FIXME: Don't convert to String here, use KString all the way.
+            auto string = String(string_or_error.value()->view());
             if (!output.try_append(move(string)))
                 return false;
         }
diff --git a/Kernel/Syscalls/hostname.cpp b/Kernel/Syscalls/hostname.cpp
index 19ca6a473c..d5ce98474a 100644
--- a/Kernel/Syscalls/hostname.cpp
+++ b/Kernel/Syscalls/hostname.cpp
@@ -32,10 +32,11 @@ KResultOr<FlatPtr> Process::sys$sethostname(Userspace<const char*> buffer, size_
     if (length > 64)
         return ENAMETOOLONG;
     return hostname().with_exclusive([&](auto& name) -> KResultOr<FlatPtr> {
-        auto copied_hostname = copy_string_from_user(buffer, length);
-        if (copied_hostname.is_null())
-            return EFAULT;
-        name = move(copied_hostname);
+        auto name_or_error = try_copy_kstring_from_user(buffer, length);
+        if (name_or_error.is_error())
+            return name_or_error.error();
+        // FIXME: Use KString instead of String here.
+        name = name_or_error.value()->view();
         return 0;
     });
 }
diff --git a/Kernel/Syscalls/module.cpp b/Kernel/Syscalls/module.cpp
index 6cd23a53d3..471dffd803 100644
--- a/Kernel/Syscalls/module.cpp
+++ b/Kernel/Syscalls/module.cpp
@@ -155,11 +155,11 @@ KResultOr<FlatPtr> Process::sys$module_unload(Userspace<const char*> user_name,
 
     REQUIRE_NO_PROMISES;
 
-    auto module_name = copy_string_from_user(user_name, name_length);
-    if (module_name.is_null())
-        return EFAULT;
+    auto module_name_or_error = try_copy_kstring_from_user(user_name, name_length);
+    if (module_name_or_error.is_error())
+        return module_name_or_error.error();
 
-    auto it = g_modules->find(module_name);
+    auto it = g_modules->find(module_name_or_error.value()->view());
     if (it == g_modules->end())
         return ENOENT;
 
diff --git a/Kernel/Syscalls/process.cpp b/Kernel/Syscalls/process.cpp
index 3a0c7acb78..200f8b1bb8 100644
--- a/Kernel/Syscalls/process.cpp
+++ b/Kernel/Syscalls/process.cpp
@@ -41,13 +41,14 @@ KResultOr<FlatPtr> Process::sys$set_process_name(Userspace<const char*> user_nam
     REQUIRE_PROMISE(proc);
     if (user_name_length > 256)
         return ENAMETOOLONG;
-    auto name = copy_string_from_user(user_name, user_name_length);
-    if (name.is_null())
-        return EFAULT;
+    auto name_or_error = try_copy_kstring_from_user(user_name, user_name_length);
+    if (name_or_error.is_error())
+        return name_or_error.error();
     // Empty and whitespace-only names only exist to confuse users.
-    if (name.is_whitespace())
+    if (name_or_error.value()->view().is_whitespace())
         return EINVAL;
-    m_name = move(name);
+    // FIXME: There's a String copy here. Process::m_name should be a KString.
+    m_name = name_or_error.value()->view();
     return 0;
 }