Support setting file mode
File mode of writable AuthFsEntry can now be changed. The mode is
maintain privately in authfs, but also pass through to fd_server.
Note that this change only aims to support getting/setting the file
mode. The mode is not currently used for ACL check.
Bug: 205169366
Test: atest AuthFsHostTest
Test: atest ComposHostTestCases
Test: composd_cmd forced-odrefresh
# exit 80 without ART hack, with permissive SELinux
Change-Id: I2405baedae9ba2be5e84eb84d3228f7be080f8c6
diff --git a/authfs/src/file/attr.rs b/authfs/src/file/attr.rs
new file mode 100644
index 0000000..48084aa
--- /dev/null
+++ b/authfs/src/file/attr.rs
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use log::error;
+use nix::sys::stat::{mode_t, Mode, SFlag};
+use std::io;
+
+use super::VirtFdService;
+
+/// Default/assumed mode of files not created by authfs.
+///
+/// For files that are given to authfs as FDs (i.e. not created through authfs), their mode is
+/// unknown (or untrusted) until it is ever set. The default mode is just to make it
+/// readable/writable to VFS. When the mode is set, the value on fd_server is supposed to become
+/// consistent.
+const DEFAULT_FILE_MODE: Mode =
+ Mode::from_bits_truncate(Mode::S_IRUSR.bits() | Mode::S_IWUSR.bits());
+
+/// Default/assumed mode of directories not created by authfs.
+///
+/// See above.
+const DEFAULT_DIR_MODE: Mode = Mode::S_IRWXU;
+
+/// `Attr` maintains the local truth for attributes (e.g. mode and type) while allowing setting the
+/// remote attribute for the file description.
+pub struct Attr {
+ service: VirtFdService,
+ mode: Mode,
+ remote_fd: i32,
+ is_dir: bool,
+}
+
+impl Attr {
+ pub fn new_file(service: VirtFdService, remote_fd: i32) -> Attr {
+ Attr { service, mode: DEFAULT_FILE_MODE, remote_fd, is_dir: false }
+ }
+
+ pub fn new_dir(service: VirtFdService, remote_fd: i32) -> Attr {
+ Attr { service, mode: DEFAULT_DIR_MODE, remote_fd, is_dir: true }
+ }
+
+ pub fn new_file_with_mode(service: VirtFdService, remote_fd: i32, mode: mode_t) -> Attr {
+ Attr { service, mode: Mode::from_bits_truncate(mode), remote_fd, is_dir: false }
+ }
+
+ pub fn new_dir_with_mode(service: VirtFdService, remote_fd: i32, mode: mode_t) -> Attr {
+ Attr { service, mode: Mode::from_bits_truncate(mode), remote_fd, is_dir: true }
+ }
+
+ pub fn mode(&self) -> u32 {
+ self.mode.bits()
+ }
+
+ /// Sets the file mode.
+ ///
+ /// In addition to the actual file mode, `encoded_mode` also contains information of the file
+ /// type.
+ pub fn set_mode(&mut self, encoded_mode: u32) -> io::Result<()> {
+ let new_sflag = SFlag::from_bits_truncate(encoded_mode);
+ let new_mode = Mode::from_bits_truncate(encoded_mode);
+
+ let type_flag = if self.is_dir { SFlag::S_IFDIR } else { SFlag::S_IFREG };
+ if !type_flag.contains(new_sflag) {
+ return Err(io::Error::from_raw_os_error(libc::EINVAL));
+ }
+
+ // Request for update only if changing.
+ if new_mode != self.mode {
+ self.service.chmod(self.remote_fd, new_mode.bits() as i32).map_err(|e| {
+ error!(
+ "Failed to chmod (fd: {}, mode: {:o}) on fd_server: {:?}",
+ self.remote_fd, new_mode, e
+ );
+ io::Error::from_raw_os_error(libc::EIO)
+ })?;
+ self.mode = new_mode;
+ }
+ Ok(())
+ }
+}