From 6b7c9f8bce4679c89f3b89cacfd4932c0aeadad4 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Sun, 25 Sep 2016 10:40:51 +0200 Subject: namespace: rework how ReadWritePaths= is applied Previously, if ReadWritePaths= was nested inside a ReadOnlyPaths= specification, then we'd first recursively apply the ReadOnlyPaths= paths, and make everything below read-only, only in order to then flip the read-only bit again for the subdirs listed in ReadWritePaths= below it. This is not only ugly (as for the dirs in question we first turn on the RO bit, only to turn it off again immediately after), but also problematic in containers, where a container manager might have marked a set of dirs read-only and this code will undo this is ReadWritePaths= is set for any. With this patch behaviour in this regard is altered: ReadOnlyPaths= will not be applied to the children listed in ReadWritePaths= in the first place, so that we do not need to turn off the RO bit for those after all. This means that ReadWritePaths=/ReadOnlyPaths= may only be used to turn on the RO bit, but never to turn it off again. Or to say this differently: if some dirs are marked read-only via some external tool, then ReadWritePaths= will not undo it. This is not only the safer option, but also more in-line with what the man page currently claims: "Entries (files or directories) listed in ReadWritePaths= are accessible from within the namespace with the same access rights as from outside." To implement this change bind_remount_recursive() gained a new "blacklist" string list parameter, which when passed may contain subdirs that shall be excluded from the read-only mounting. A number of functions are updated to add more debug logging to make this more digestable. --- src/nspawn/nspawn-mount.c | 6 +++--- src/nspawn/nspawn.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) (limited to 'src/nspawn') diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c index 295b75341f..8457357003 100644 --- a/src/nspawn/nspawn-mount.c +++ b/src/nspawn/nspawn-mount.c @@ -476,7 +476,7 @@ static int mount_bind(const char *dest, CustomMount *m) { return log_error_errno(errno, "mount(%s) failed: %m", where); if (m->read_only) { - r = bind_remount_recursive(where, true); + r = bind_remount_recursive(where, true, NULL); if (r < 0) return log_error_errno(r, "Read-only bind mount failed: %m"); } @@ -990,7 +990,7 @@ int setup_volatile_state( /* --volatile=state means we simply overmount /var with a tmpfs, and the rest read-only. */ - r = bind_remount_recursive(directory, true); + r = bind_remount_recursive(directory, true, NULL); if (r < 0) return log_error_errno(r, "Failed to remount %s read-only: %m", directory); @@ -1065,7 +1065,7 @@ int setup_volatile( bind_mounted = true; - r = bind_remount_recursive(t, true); + r = bind_remount_recursive(t, true, NULL); if (r < 0) { log_error_errno(r, "Failed to remount %s read-only: %m", t); goto fail; diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c index 0d61d34ebf..1f3e1f2dac 100644 --- a/src/nspawn/nspawn.c +++ b/src/nspawn/nspawn.c @@ -3019,7 +3019,7 @@ static int outer_child( return r; if (arg_read_only) { - r = bind_remount_recursive(directory, true); + r = bind_remount_recursive(directory, true, NULL); if (r < 0) return log_error_errno(r, "Failed to make tree read-only: %m"); } -- cgit v1.2.3-54-g00ecf