From: Yu Watanabe Date: Wed, 11 Oct 2023 05:57:54 +0000 (+0900) Subject: core/namespace: unify logic of mounting /proc and /sys X-Git-Tag: v255-rc1~130^2~2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b18f4eedebf5c397f7ea2f6620626114ad8bbaba;p=thirdparty%2Fsystemd.git core/namespace: unify logic of mounting /proc and /sys No functional change, just refactoring. --- diff --git a/src/core/namespace.c b/src/core/namespace.c index cae082c655c..9202fbc1b73 100644 --- a/src/core/namespace.c +++ b/src/core/namespace.c @@ -1160,37 +1160,64 @@ static int mount_bind_sysfs(const MountEntry *m) { return mount_nofollow_verbose(LOG_DEBUG, "/sys", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL); } -static int mount_private_sysfs(const MountEntry *m) { - const char *entry_path = mount_entry_path(ASSERT_PTR(m)); +static int mount_private_apivfs( + const char *fstype, + const char *entry_path, + const char *bind_source, + const char *opts) { + int r, n; - (void) mkdir_p_label(entry_path, 0755); + assert(fstype); + assert(entry_path); + assert(bind_source); - n = umount_recursive(entry_path, 0); + (void) mkdir_p_label(entry_path, 0755); + n = umount_recursive(entry_path, /* flags = */ 0); - r = mount_nofollow_verbose(LOG_DEBUG, "sysfs", entry_path, "sysfs", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL); + r = mount_nofollow_verbose(LOG_DEBUG, fstype, entry_path, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts); + if (r == -EINVAL && opts) + /* If this failed with EINVAL then this likely means the textual hidepid= stuff for procfs is + * not supported by the kernel, and thus the per-instance hidepid= neither, which means we + * really don't want to use it, since it would affect our host's /proc mount. Hence let's + * gracefully fallback to a classic, unrestricted version. */ + r = mount_nofollow_verbose(LOG_DEBUG, fstype, entry_path, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, /* opts = */ NULL); if (ERRNO_IS_NEG_PRIVILEGE(r)) { - /* When we do not have enough privileges to mount sysfs, fall back to use existing /sys. */ + /* When we do not have enough privileges to mount a new instance, fall back to use an + * existing mount. */ if (n > 0) - /* /sys or some of sub-mounts are umounted in the above. Refuse incomplete tree. + /* The mount or some of sub-mounts are umounted in the above. Refuse incomplete tree. * Propagate the original error code returned by mount() in the above. */ return r; - return mount_bind_sysfs(m); + r = path_is_mount_point(entry_path, /* root = */ NULL, /* flags = */ 0); + if (r < 0) + return log_debug_errno(r, "Unable to determine whether '%s' is already mounted: %m", entry_path); + if (r > 0) + return 0; /* Use the current mount as is. */ + + /* We lack permissions to mount a new instance, and it is not already mounted. But we can + * access the host's, so as a final fallback bind-mount it to the destination, as most likely + * we are inside a user manager in an unprivileged user namespace. */ + return mount_nofollow_verbose(LOG_DEBUG, bind_source, entry_path, /* fstype = */ NULL, MS_BIND|MS_REC, /* opts = */ NULL); } else if (r < 0) return r; - /* We mounted a new instance now. Let's bind mount the children over now. */ - (void) bind_mount_submounts("/sys", entry_path); + /* We mounted a new instance now. Let's bind mount the children over now. This matters for nspawn + * where a bunch of files are overmounted, in particular the boot id. */ + (void) bind_mount_submounts(bind_source, entry_path); return 0; } +static int mount_private_sysfs(const MountEntry *m) { + assert(m); + return mount_private_apivfs("sysfs", mount_entry_path(m), "/sys", /* opts = */ NULL); +} + static int mount_procfs(const MountEntry *m, const NamespaceParameters *p) { _cleanup_free_ char *opts = NULL; - const char *entry_path; - int r, n; assert(m); assert(p); @@ -1226,49 +1253,11 @@ static int mount_procfs(const MountEntry *m, const NamespaceParameters *p) { return -ENOMEM; } - entry_path = mount_entry_path(m); - (void) mkdir_p_label(entry_path, 0755); - /* Mount a new instance, so that we get the one that matches our user namespace, if we are running in * one. i.e we don't reuse existing mounts here under any condition, we want a new instance owned by * our user namespace and with our hidepid= settings applied. Hence, let's get rid of everything * mounted on /proc/ first. */ - - n = umount_recursive(entry_path, 0); - - r = mount_nofollow_verbose(LOG_DEBUG, "proc", entry_path, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, opts); - if (r == -EINVAL && opts) - /* If this failed with EINVAL then this likely means the textual hidepid= stuff is - * not supported by the kernel, and thus the per-instance hidepid= neither, which - * means we really don't want to use it, since it would affect our host's /proc - * mount. Hence let's gracefully fallback to a classic, unrestricted version. */ - r = mount_nofollow_verbose(LOG_DEBUG, "proc", entry_path, "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL); - if (ERRNO_IS_NEG_PRIVILEGE(r)) { - /* When we do not have enough privileges to mount /proc, fall back to use existing /proc. */ - - if (n > 0) - /* /proc or some of sub-mounts are umounted in the above. Refuse incomplete tree. - * Propagate the original error code returned by mount() in the above. */ - return r; - - r = path_is_mount_point(entry_path, NULL, 0); - if (r < 0) - return log_debug_errno(r, "Unable to determine whether /proc is already mounted: %m"); - if (r > 0) - return 0; - - /* We lack permissions to mount a new instance of /proc, and it is not already mounted. But - * we can access the host's, so as a final fallback bind-mount it to the destination, as most - * likely we are inside a user manager in an unprivileged user namespace. */ - return mount_nofollow_verbose(LOG_DEBUG, "/proc", entry_path, NULL, MS_BIND|MS_REC, NULL); - - } else if (r < 0) - return r; - - /* We mounted a new instance now. Let's bind mount the children over now. This matters for nspawn - * where a bunch of files are overmounted, in particular the boot id */ - (void) bind_mount_submounts("/proc", entry_path); - return 0; + return mount_private_apivfs("proc", mount_entry_path(m), "/proc", opts); } static int mount_tmpfs(const MountEntry *m) {