From 2b8d586c5a10e9574acd1ae49a60cbf11cf22830 Mon Sep 17 00:00:00 2001

From: Colin Walters <walters@verbum.org>

Date: Mon, 29 Jan 2018 13:48:02 +0100

Subject: [PATCH] switchroot: Ensure /sysroot is set to "private" propagation

Downstream BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1498281

This came up as a problem with `oci-umount` which was trying to ensure some host

mounts like `/var/lib/containers` don't leak into privileged containers.  But

since our `/sysroot` mount wasn't private we also got a copy there.

We should have done this from the very start - it makes `findmnt` way, way less

ugly and is just the obviously right thing to do, will possibly create world

peace etc.

Closes: #1438

Approved by: rhvgoyal

---

 src/switchroot/ostree-prepare-root.c | 11 +++++++++++

 src/switchroot/ostree-remount.c      |  9 +++++++++

 2 files changed, 20 insertions(+)

diff --git a/src/switchroot/ostree-prepare-root.c b/src/switchroot/ostree-prepare-root.c

index 43e15fcc..671a6a26 100644

--- a/src/switchroot/ostree-prepare-root.c

+++ b/src/switchroot/ostree-prepare-root.c

@@ -244,6 +244,17 @@ main(int argc, char *argv[])

         err (EXIT_FAILURE, "failed to MS_MOVE %s to %s", deploy_path, root_mountpoint);

     }

+  /* The /sysroot mount needs to be private to avoid having a mount for e.g. /var/cache

+   * also propagate to /sysroot/ostree/deploy/$stateroot/var/cache

+   *

+   * Now in reality, today this is overridden by systemd: the *actual* way we fix this up

+   * is in ostree-remount.c.  But let's do it here to express the semantics we want

+   * at the very start (perhaps down the line systemd will have compile/runtime option

+   * to say that the initramfs environment did everything right from the start).

+   */

+  if (mount ("none", "sysroot", NULL, MS_PRIVATE, NULL) < 0)

+    err (EXIT_FAILURE, "remounting 'sysroot' private");

+

   if (getpid() == 1)

     {

       execl ("/sbin/init", "/sbin/init", NULL);

diff --git a/src/switchroot/ostree-remount.c b/src/switchroot/ostree-remount.c

index fe6b6f44..cc2b81b3 100644

--- a/src/switchroot/ostree-remount.c

+++ b/src/switchroot/ostree-remount.c

@@ -44,6 +44,15 @@ main(int argc, char *argv[])

   struct stat stbuf;

   int i;

+  /* The /sysroot mount needs to be private to avoid having a mount for e.g. /var/cache

+   * also propagate to /sysroot/ostree/deploy/$stateroot/var/cache

+   *

+   * Today systemd remounts / (recursively) as shared, so we're undoing that as early

+   * as possible.  See also a copy of this in ostree-prepare-root.c.

+   */

+  if (mount ("none", "/sysroot", NULL, MS_REC | MS_PRIVATE, NULL) < 0)

+    perror ("warning: While remounting /sysroot MS_PRIVATE");

+

   if (path_is_on_readonly_fs ("/"))

     {

       /* If / isn't writable, don't do any remounts; we don't want

-- 

2.14.3