/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #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; }