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/* 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 usecase 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;
}
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