Kernel+LibC+LibCore: Add lchown and fchownat functions

This modifies sys$chown to allow specifying whether or not to follow
symlinks and in which directory.

This was then used to implement lchown and fchownat in LibC and LibCore.

1 files changed, 14 insertions, 1 deletions

diff --git a/Kernel/Syscalls/chown.cpp b/Kernel/Syscalls/chown.cpp
index 92172fed61..0db2c9cccc 100644
--- a/Kernel/Syscalls/chown.cpp
+++ b/Kernel/Syscalls/chown.cpp
@@ -4,6 +4,8 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/NonnullRefPtrVector.h>
+#include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/OpenFileDescription.h>
 #include <Kernel/Process.h>
 
@@ -24,7 +26,18 @@ ErrorOr<FlatPtr> Process::sys$chown(Userspace<const Syscall::SC_chown_params*> u
     TRY(require_promise(Pledge::chown));
     auto params = TRY(copy_typed_from_user(user_params));
     auto path = TRY(get_syscall_path_argument(params.path));
-    TRY(VirtualFileSystem::the().chown(path->view(), params.uid, params.gid, current_directory()));
+
+    RefPtr<Custody> base;
+    if (params.dirfd == AT_FDCWD) {
+        base = current_directory();
+    } else {
+        auto base_description = TRY(fds().open_file_description(params.dirfd));
+        if (!base_description->custody())
+            return EINVAL;
+        base = base_description->custody();
+    }
+
+    TRY(VirtualFileSystem::the().chown(path->view(), params.uid, params.gid, *base, params.follow_symlinks ? 0 : O_NOFOLLOW_NOERROR));
     return 0;
 }