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-rw-r--r--src/shared/install-file.c270
1 files changed, 270 insertions, 0 deletions
diff --git a/src/shared/install-file.c b/src/shared/install-file.c
new file mode 100644
index 0000000..3b4d651
--- /dev/null
+++ b/src/shared/install-file.c
@@ -0,0 +1,270 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/ioctl.h>
+
+#include "btrfs-util.h"
+#include "chattr-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fs-util.h"
+#include "install-file.h"
+#include "missing_syscall.h"
+#include "rm-rf.h"
+#include "sync-util.h"
+
+int fs_make_very_read_only(int fd) {
+ struct stat st;
+ int r;
+
+ assert(fd >= 0);
+
+ /* Tries to make the specified fd "comprehensively" read-only. Primary use case for this is OS images,
+ * i.e. either loopback files or larger directory hierarchies. Depending on the inode type and
+ * backing file system this means something different:
+ *
+ * 1. If the fd refers to a btrfs subvolume we'll mark it read-only as a whole
+ * 2. If the fd refers to any other directory we'll set the FS_IMMUTABLE_FL flag on it
+ * 3. If the fd refers to a regular file we'll drop the w bits.
+ * 4. If the fd refers to a block device, use BLKROSET to set read-only state
+ *
+ * You might wonder why not drop the x bits for directories. That's because we want to guarantee that
+ * everything "inside" the image remains largely the way it is, in case you mount it. And since the
+ * mode of the root dir of the image is pretty visible we don't want to modify it. btrfs subvol flags
+ * and the FS_IMMUTABLE_FL otoh are much less visible. Changing the mode of regular files should be
+ * OK though, since after all this is supposed to be used for disk images, i.e. the fs in the disk
+ * image doesn't make the mode of the loopback file it is stored in visible. */
+
+ if (fstat(fd, &st) < 0)
+ return -errno;
+
+ switch (st.st_mode & S_IFMT) {
+
+ case S_IFDIR:
+ if (btrfs_might_be_subvol(&st)) {
+ r = btrfs_subvol_set_read_only_fd(fd, true);
+ if (r >= 0)
+ return 0;
+
+ if (!ERRNO_IS_NOT_SUPPORTED(r) && r != -EINVAL)
+ return r;
+ }
+
+ r = chattr_fd(fd, FS_IMMUTABLE_FL, FS_IMMUTABLE_FL, NULL);
+ if (r < 0)
+ return r;
+
+ break;
+
+ case S_IFREG:
+ if ((st.st_mode & 0222) != 0)
+ if (fchmod(fd, st.st_mode & 07555) < 0)
+ return -errno;
+
+ break;
+
+ case S_IFBLK: {
+ int ro = 1;
+
+ if (ioctl(fd, BLKROSET, &ro) < 0)
+ return -errno;
+
+ break;
+ }
+
+ default:
+ return -EBADFD;
+ }
+
+ return 0;
+}
+
+static int unlinkat_maybe_dir(int dirfd, const char *pathname) {
+
+ /* Invokes unlinkat() for regular files first, and if this fails with EISDIR tries again with
+ * AT_REMOVEDIR */
+
+ if (unlinkat(dirfd, pathname, 0) < 0) {
+ if (errno != EISDIR)
+ return -errno;
+
+ if (unlinkat(dirfd, pathname, AT_REMOVEDIR) < 0)
+ return -errno;
+ }
+
+ return 0;
+}
+
+int install_file(int source_atfd, const char *source_name,
+ int target_atfd, const char *target_name,
+ InstallFileFlags flags) {
+
+ _cleanup_close_ int rofd = -EBADF;
+ int r;
+
+ /* Moves a file or directory tree into place, with some bells and whistles:
+ *
+ * 1. Optionally syncs before/after to ensure file installation can be used as barrier
+ * 2. Optionally marks the file/directory read-only using fs_make_very_read_only()
+ * 3. Optionally operates in replacing or in non-replacing mode.
+ * 4. If it replaces will remove the old tree if needed.
+ */
+
+ assert(source_atfd >= 0 || source_atfd == AT_FDCWD);
+ assert(source_name);
+ assert(target_atfd >= 0 || target_atfd == AT_FDCWD);
+
+ /* If target_name is specified as NULL no renaming takes place. Instead it is assumed the file is
+ * already in place, and only the syncing/read-only marking shall be applied. Note that with
+ * target_name=NULL and flags=0 this call is a NOP */
+
+ if ((flags & (INSTALL_FSYNC|INSTALL_FSYNC_FULL|INSTALL_SYNCFS|INSTALL_READ_ONLY)) != 0) {
+ _cleanup_close_ int pfd = -EBADF;
+ struct stat st;
+
+ /* Open an O_PATH fd for the source if we need to sync things or mark things read only. */
+
+ pfd = openat(source_atfd, source_name, O_PATH|O_CLOEXEC|O_NOFOLLOW);
+ if (pfd < 0)
+ return -errno;
+
+ if (fstat(pfd, &st) < 0)
+ return -errno;
+
+ switch (st.st_mode & S_IFMT) {
+
+ case S_IFREG: {
+ _cleanup_close_ int regfd = -EBADF;
+
+ regfd = fd_reopen(pfd, O_RDONLY|O_CLOEXEC);
+ if (regfd < 0)
+ return regfd;
+
+ if ((flags & (INSTALL_FSYNC_FULL|INSTALL_SYNCFS)) != 0) {
+ /* If this is just a regular file (as oppose to a fully populated directory)
+ * let's downgrade INSTALL_SYNCFS to INSTALL_FSYNC_FULL, after all this is
+ * going to be a single inode we install */
+ r = fsync_full(regfd);
+ if (r < 0)
+ return r;
+ } else if (flags & INSTALL_FSYNC) {
+ if (fsync(regfd) < 0)
+ return -errno;
+ }
+
+ if (flags & INSTALL_READ_ONLY)
+ rofd = TAKE_FD(regfd);
+
+ break;
+ }
+
+ case S_IFDIR: {
+ _cleanup_close_ int dfd = -EBADF;
+
+ dfd = fd_reopen(pfd, O_RDONLY|O_DIRECTORY|O_CLOEXEC);
+ if (dfd < 0)
+ return dfd;
+
+ if (flags & INSTALL_SYNCFS) {
+ if (syncfs(dfd) < 0)
+ return -errno;
+ } else if (flags & INSTALL_FSYNC_FULL) {
+ r = fsync_full(dfd);
+ if (r < 0)
+ return r;
+ } else if (flags & INSTALL_FSYNC) {
+ if (fsync(dfd) < 0)
+ return -errno;
+ }
+
+ if (flags & INSTALL_READ_ONLY)
+ rofd = TAKE_FD(dfd);
+
+ break;
+ }
+
+ default:
+ /* Other inodes: char/block device inodes, fifos, symlinks, sockets don't need
+ * syncing themselves, as they only exist in the directory, and have no contents on
+ * disk */
+
+ if (target_name && (flags & (INSTALL_FSYNC_FULL|INSTALL_SYNCFS)) != 0) {
+ r = fsync_directory_of_file(pfd);
+ if (r < 0)
+ return r;
+ }
+
+ break;
+ }
+ }
+
+ if (target_name) {
+ /* Rename the file */
+
+ if (flags & INSTALL_REPLACE) {
+ /* First, try a simple renamat(), maybe that's enough */
+ if (renameat(source_atfd, source_name, target_atfd, target_name) < 0) {
+ _cleanup_close_ int dfd = -EBADF;
+
+ if (!IN_SET(errno, EEXIST, ENOTDIR, ENOTEMPTY, EISDIR, EBUSY))
+ return -errno;
+
+ /* Hmm, the target apparently existed already. Let's try to use
+ * RENAME_EXCHANGE. But let's first open the inode if it's a directory, so
+ * that we can later remove its contents if it's a directory. Why do this
+ * before the rename()? Mostly because if we have trouble opening the thing
+ * we want to know before we start actually modifying the file system. */
+
+ dfd = openat(target_atfd, target_name, O_RDONLY|O_DIRECTORY|O_CLOEXEC, 0);
+ if (dfd < 0 && errno != ENOTDIR)
+ return -errno;
+
+ if (renameat2(source_atfd, source_name, target_atfd, target_name, RENAME_EXCHANGE) < 0) {
+
+ if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL)
+ return -errno;
+
+ /* The exchange didn't work, let's remove the target first, and try again */
+
+ if (dfd >= 0)
+ (void) rm_rf_children(TAKE_FD(dfd), REMOVE_PHYSICAL|REMOVE_SUBVOLUME|REMOVE_CHMOD, NULL);
+
+ r = unlinkat_maybe_dir(target_atfd, target_name);
+ if (r < 0)
+ return log_debug_errno(r, "Failed to remove target directory: %m");
+
+ if (renameat(source_atfd, source_name, target_atfd, target_name) < 0)
+ return -errno;
+ } else {
+ /* The exchange worked, hence let's remove the source (i.e. the old target) */
+ if (dfd >= 0)
+ (void) rm_rf_children(TAKE_FD(dfd), REMOVE_PHYSICAL|REMOVE_SUBVOLUME|REMOVE_CHMOD, NULL);
+
+ r = unlinkat_maybe_dir(source_atfd, source_name);
+ if (r < 0)
+ return log_debug_errno(r, "Failed to remove replaced target directory: %m");
+ }
+ }
+ } else {
+ r = rename_noreplace(source_atfd, source_name, target_atfd, target_name);
+ if (r < 0)
+ return r;
+ }
+ }
+
+ if (rofd >= 0) {
+ r = fs_make_very_read_only(rofd);
+ if (r < 0)
+ return r;
+ }
+
+ if ((flags & (INSTALL_FSYNC_FULL|INSTALL_SYNCFS)) != 0) {
+ if (target_name)
+ r = fsync_parent_at(target_atfd, target_name);
+ else
+ r = fsync_parent_at(source_atfd, source_name);
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-19 23:38:22 +0000