+/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
#include <fcntl.h>
#include <linux/magic.h>
-#ifdef HAVE_ACL
+#if HAVE_ACL
#include <sys/acl.h>
#endif
#include <sys/stat.h>
+#include <sys/statvfs.h>
#include <sys/vfs.h>
#include <unistd.h>
#include "acl-util.h"
#include "dirent-util.h"
#include "fd-util.h"
+#include "fs-util.h"
#include "missing.h"
+#include "nspawn-def.h"
#include "nspawn-patch-uid.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "strv.h"
#include "user-util.h"
-#ifdef HAVE_ACL
+#if HAVE_ACL
static int get_acl(int fd, const char *name, acl_type_t type, acl_t *ret) {
char procfs_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
return -errno;
/* The Linux kernel alters the mode in some cases of chown(). Let's undo this. */
- if (name && !S_ISLNK(st->st_mode))
- r = fchmodat(fd, name, st->st_mode, 0);
- else
+ if (name) {
+ if (!S_ISLNK(st->st_mode))
+ r = fchmodat(fd, name, st->st_mode, 0);
+ else /* AT_SYMLINK_NOFOLLOW is not available for fchmodat() */
+ r = 0;
+ } else
r = fchmod(fd, st->st_mode);
if (r < 0)
return -errno;
return r > 0 || changed;
}
-static int is_procfs_sysfs_or_suchlike(int fd) {
+/*
+ * Check if the filesystem is fully compatible with user namespaces or
+ * UID/GID patching. Some filesystems in this list can be fully mounted inside
+ * user namespaces, however their inodes may relate to host resources or only
+ * valid in the global user namespace, therefore no patching should be applied.
+ */
+static int is_fs_fully_userns_compatible(const struct statfs *sfs) {
+
+ assert(sfs);
+
+ return F_TYPE_EQUAL(sfs->f_type, BINFMTFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, CGROUP_SUPER_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, CGROUP2_SUPER_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, DEBUGFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, DEVPTS_SUPER_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, EFIVARFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, HUGETLBFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, MQUEUE_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, PROC_SUPER_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, PSTOREFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, SELINUX_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, SMACK_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, SECURITYFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, BPF_FS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, TRACEFS_MAGIC) ||
+ F_TYPE_EQUAL(sfs->f_type, SYSFS_MAGIC);
+}
+
+static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift, bool is_toplevel) {
+ _cleanup_closedir_ DIR *d = NULL;
+ bool changed = false;
struct statfs sfs;
+ int r;
assert(fd >= 0);
if (fstatfs(fd, &sfs) < 0)
return -errno;
- return F_TYPE_EQUAL(sfs.f_type, BINFMTFS_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, CGROUP_SUPER_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, CGROUP2_SUPER_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, DEBUGFS_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, DEVPTS_SUPER_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, EFIVARFS_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, HUGETLBFS_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, MQUEUE_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, PROC_SUPER_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, PSTOREFS_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, SELINUX_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, SMACK_MAGIC) ||
- F_TYPE_EQUAL(sfs.f_type, SYSFS_MAGIC);
-}
-
-static int recurse_fd(int fd, bool donate_fd, const struct stat *st, uid_t shift) {
- bool changed = false;
- int r;
-
- assert(fd >= 0);
+ /* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we probably
+ * shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's stop the recursion
+ * when we hit procfs, sysfs or some other special file systems. */
- /* We generally want to permit crossing of mount boundaries when patching the UIDs/GIDs. However, we
- * probably shouldn't do this for /proc and /sys if that is already mounted into place. Hence, let's
- * stop the recursion when we hit a procfs or sysfs file system. */
- r = is_procfs_sysfs_or_suchlike(fd);
+ r = is_fs_fully_userns_compatible(&sfs);
if (r < 0)
goto finish;
if (r > 0) {
goto finish;
}
- r = patch_fd(fd, NULL, st, shift);
- if (r < 0)
- goto finish;
+ /* Also, if we hit a read-only file system, then don't bother, skip the whole subtree */
+ if ((sfs.f_flags & ST_RDONLY) ||
+ access_fd(fd, W_OK) == -EROFS)
+ goto read_only;
if (S_ISDIR(st->st_mode)) {
- _cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
if (!donate_fd) {
FOREACH_DIRENT_ALL(de, d, r = -errno; goto finish) {
struct stat fst;
- if (STR_IN_SET(de->d_name, ".", ".."))
+ if (dot_or_dot_dot(de->d_name))
continue;
if (fstatat(dirfd(d), de->d_name, &fst, AT_SYMLINK_NOFOLLOW) < 0) {
}
- r = recurse_fd(subdir_fd, true, &fst, shift);
+ r = recurse_fd(subdir_fd, true, &fst, shift, false);
if (r < 0)
goto finish;
if (r > 0)
}
}
+ /* After we descended, also patch the directory itself. It's key to do this in this order so that the top-level
+ * directory is patched as very last object in the tree, so that we can use it as quick indicator whether the
+ * tree is properly chown()ed already. */
+ r = patch_fd(d ? dirfd(d) : fd, NULL, st, shift);
+ if (r == -EROFS)
+ goto read_only;
+ if (r > 0)
+ changed = true;
+
r = changed;
+ goto finish;
+
+read_only:
+ if (!is_toplevel) {
+ _cleanup_free_ char *name = NULL;
+
+ /* When we hit a ready-only subtree we simply skip it, but log about it. */
+ (void) fd_get_path(fd, &name);
+ log_debug("Skippping read-only file or directory %s.", strna(name));
+ r = changed;
+ }
finish:
if (donate_fd)
goto finish;
}
+ if (shift == UID_BUSY_BASE) {
+ r = -EINVAL;
+ goto finish;
+ }
+
if (range != 0x10000) {
/* We only support containers with 16bit UID ranges for the patching logic */
r = -EOPNOTSUPP;
if (((uint32_t) (st.st_uid ^ shift) >> 16) == 0)
return 0;
- return recurse_fd(fd, donate_fd, &st, shift);
+ /* Before we start recursively chowning, mark the top-level dir as "busy" by chowning it to the "busy"
+ * range. Should we be interrupted in the middle of our work, we'll see it owned by this user and will start
+ * chown()ing it again, unconditionally, as the busy UID is not a valid UID we'd everpick for ourselves. */
+
+ if ((st.st_uid & UID_BUSY_MASK) != UID_BUSY_BASE) {
+ if (fchown(fd,
+ UID_BUSY_BASE | (st.st_uid & ~UID_BUSY_MASK),
+ (gid_t) UID_BUSY_BASE | (st.st_gid & ~(gid_t) UID_BUSY_MASK)) < 0) {
+ r = -errno;
+ goto finish;
+ }
+ }
+
+ return recurse_fd(fd, donate_fd, &st, shift, true);
finish:
if (donate_fd)
projects / thirdparty / systemd.git / blobdiff