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