Kernel: Make O_RDONLY non-zero

Sergey suggested that having a non-zero O_RDONLY would make some things
less confusing, and it seems like he's right about that.

We can now easily check read/write permissions separately instead of
dancing around with the bits.

This patch also fixes unveil() validation for O_RDWR which previously
forgot to check for "r" permission.

Kernel/FileSystem/FileDescription.h

@@ -59,16 +59,8 @@ class FileDescription : public RefCounted<FileDescription> {
 
  void set_rw_mode(int options)
  {
- if (options & O_WRONLY) {
- set_readable(false);
- set_writable(true);
- } else if (options & O_RDWR) {
- set_readable(true);
- set_writable(true);
- } else {
- set_readable(true);
- set_writable(false);
- }
+ set_readable(options & O_RDONLY);
+ set_writable(options & O_WRONLY);
  }
 
  int close();

Kernel/FileSystem/VirtualFileSystem.cpp

@@ -239,13 +239,10 @@ KResultOr<NonnullRefPtr<FileDescription>> VFS::open(StringView path, int options
 
  bool should_truncate_file = false;
 
- // NOTE: Read permission is a bit weird, since O_RDONLY == 0,
- // so we check if (NOT write_only OR read_and_write)
- if (!(options & O_WRONLY) || (options & O_RDWR)) {
- if (!metadata.may_read(current->process()))
- return KResult(-EACCES);
- }
- if ((options & O_WRONLY) || (options & O_RDWR)) {
+ if ((options & O_RDONLY) && !metadata.may_read(current->process()))
+ return KResult(-EACCES);
+
+ if (options & O_WRONLY) {
  if (!metadata.may_write(current->process()))
  return KResult(-EACCES);
  if (metadata.is_directory())
@@ -748,21 +745,23 @@ KResult VFS::validate_path_against_process_veil(StringView path, int options)
  }
  return KSuccess;
  }
- if ((options & O_RDWR) || (options & O_WRONLY)) {
+ if (options & O_RDONLY) {
+ if (!(unveiled_path->permissions & UnveiledPath::Access::Read)) {
+ dbg() << *current << " rejecting path '" << path << "' since it hasn't been unveiled with 'r' permission.";
+ return KResult(-EACCES);
+ }
+ }
+ if (options & O_WRONLY) {
  if (!(unveiled_path->permissions & UnveiledPath::Access::Write)) {
  dbg() << *current << " rejecting path '" << path << "' since it hasn't been unveiled with 'w' permission.";
  return KResult(-EACCES);
  }
- } else if (options & O_EXEC) {
+ }
+ if (options & O_EXEC) {
  if (!(unveiled_path->permissions & UnveiledPath::Access::Execute)) {
  dbg() << *current << " rejecting path '" << path << "' since it hasn't been unveiled with 'x' permission.";
  return KResult(-EACCES);
  }
- } else {
- if (!(unveiled_path->permissions & UnveiledPath::Access::Read)) {
- dbg() << *current << " rejecting path '" << path << "' since it hasn't been unveiled with 'r' permission.";
- return KResult(-EACCES);
- }
  }
  return KSuccess;
 }

Kernel/FileSystem/VirtualFileSystem.h

@@ -38,9 +38,9 @@
 #include <Kernel/FileSystem/InodeMetadata.h>
 #include <Kernel/KResult.h>
 
-#define O_RDONLY 0
-#define O_WRONLY 1
-#define O_RDWR 2
+#define O_RDONLY 1
+#define O_WRONLY 2
+#define O_RDWR 3
 #define O_EXEC 4
 #define O_CREAT 0100
 #define O_EXCL 0200

Kernel/Net/LocalSocket.cpp

@@ -111,7 +111,7 @@ KResult LocalSocket::bind(const sockaddr* user_address, socklen_t address_size)
 
  mode_t mode = S_IFSOCK | (m_prebind_mode & 04777);
  UidAndGid owner { m_prebind_uid, m_prebind_gid };
- auto result = VFS::the().open(path, O_RDWR | O_CREAT | O_EXCL | O__NOERROR, mode, current->process().current_directory(), owner);
+ auto result = VFS::the().open(path, O_CREAT | O_EXCL | O__NOERROR, mode, current->process().current_directory(), owner);
  if (result.is_error()) {
  if (result.error() == -EEXIST)
  return KResult(-EADDRINUSE);

Kernel/Process.cpp

@@ -1945,9 +1945,9 @@ int Process::sys$open(const Syscall::SC_open_params* user_params)
  if (options & O_UNLINK_INTERNAL)
  return -EINVAL;
 
- if ((options & O_RDWR) || (options & O_WRONLY))
+ if (options & O_WRONLY)
  REQUIRE_PROMISE(wpath);
- else
+ else if (options & O_RDONLY)
  REQUIRE_PROMISE(rpath);
 
  if (options & O_CREAT)

Libraries/LibC/fcntl.h

@@ -39,9 +39,9 @@ __BEGIN_DECLS
 
 #define FD_CLOEXEC 1
 
-#define O_RDONLY 0
-#define O_WRONLY 1
-#define O_RDWR 2
+#define O_RDONLY 1
+#define O_WRONLY 2
+#define O_RDWR 3
 #define O_ACCMODE 3
 #define O_EXEC 4
 #define O_CREAT 0100