From baec9e2d2d2b8a082ff3ebd1ac621f6d96eaf94d Mon Sep 17 00:00:00 2001
From: Brian Gianforcaro <bgianf@serenityos.org>
Date: Fri, 23 Jul 2021 08:21:10 -0700
Subject: [PATCH] Kernel: Migrate sys$unveil to use the KString API

This avoids potential unhandled OOM that's possible with the old
copy_string_from_user API.
---
 Kernel/Syscalls/unveil.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/Kernel/Syscalls/unveil.cpp b/Kernel/Syscalls/unveil.cpp
index 8d0d498f5e..7c7bfb7b95 100644
--- a/Kernel/Syscalls/unveil.cpp
+++ b/Kernel/Syscalls/unveil.cpp
@@ -53,13 +53,17 @@ KResultOr<FlatPtr> Process::sys$unveil(Userspace<const Syscall::SC_unveil_params
     if (path.is_empty() || !path.view().starts_with('/'))
         return EINVAL;
 
-    auto permissions = copy_string_from_user(params.permissions);
-    if (permissions.is_null())
-        return EFAULT;
+    OwnPtr<KString> permissions;
+    {
+        auto permissions_or_error = try_copy_kstring_from_user(params.permissions);
+        if (permissions_or_error.is_error())
+            return permissions_or_error.error();
+        permissions = permissions_or_error.release_value();
+    }
 
     // Let's work out permissions first...
     unsigned new_permissions = 0;
-    for (const char permission : permissions) {
+    for (const char permission : permissions->view()) {
         switch (permission) {
         case 'r':
             new_permissions |= UnveilAccess::Read;