In -U mode we might need to re-chown() all files and directories to
match the UID shift we want for the image. That's problematic on fat
partitions, such as the ESP (and which is generated by mkosi's
--bootable switch), because fat of course knows no UID/GID file
ownership natively.
With this change we take benefit of the uid= and gid= mount options FAT
knows: instead of chown()ing all files and directories we can just
specify the right UID/GID to use at mount time.
This beefs up the image dissection logic in two ways:
1. First of all support for mounting relevant file systems with
uid=/gid= is added: when a UID is specified during mount it is used for
all applicable file systems.
2. Secondly, two new mount flags are added:
DISSECT_IMAGE_MOUNT_ROOT_ONLY and DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY.
If one is specified the mount routine will either only mount the root
partition of an image, or all partitions except the root partition.
This is used by nspawn: first the root partition is mounted, so that
we can determine the UID shift in use so far, based on ownership of
the image's root directory. Then, we mount the remaining partitions
in a second go, this time with the right UID/GID information.
This is a simple wrapper around name_to_handle_at_loop() and
fd_fdinfo_mnt_id() to query the mnt ID of a path. It uses
name_to_handle_at() where it can, and falls back to to
fd_fdinfo_mnt_id() where that doesn't work.
This is a best-effort thing of course, since neither name_to_handle_at()
nor the fdinfo logic work on all kernels.
As it turns out MAX_HANDLE_SZ is a lie, the handle buffer we pass into
name_to_handle_at() might need to be larger than MAX_HANDLE_SZ, and we
thus need to invoke name_to_handle_at() in a loop, growing the buffer as
needed.
This adds a new wrapper name_to_handle_at_loop() around
name_to_handle_at() that does the necessary looping, and ports over all
users.
Fixes: #7082
Enable masking the /proc folder using the 'InaccessiblePaths' unit
option.
This also slightly simplify mounts setup as the bind_remount_recursive
function will only open /proc/self/mountinfo once.
This is based on the suggestion at:
https://lists.freedesktop.org/archives/systemd-devel/2017-April/038634.html
Let's use chase_symlinks() everywhere, and stop using GNU
canonicalize_file_name() everywhere. For most cases this should not change
behaviour, however increase exposure of our function to get better tested. Most
importantly in a few cases (most notably nspawn) it can take the correct root
directory into account when chasing symlinks.
This makes it easier to debug failed nspawn invocations:
Mounting sysfs on /var/lib/machines/fedora-rawhide/sys (MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV "")...
Mounting tmpfs on /var/lib/machines/fedora-rawhide/dev (MS_NOSUID|MS_STRICTATIME "mode=755,uid=1450901504,gid=1450901504")...
Mounting tmpfs on /var/lib/machines/fedora-rawhide/dev/shm (MS_NOSUID|MS_NODEV|MS_STRICTATIME "mode=1777,uid=1450901504,gid=1450901504")...
Mounting tmpfs on /var/lib/machines/fedora-rawhide/run (MS_NOSUID|MS_NODEV|MS_STRICTATIME "mode=755,uid=1450901504,gid=1450901504")...
Bind-mounting /sys/fs/selinux on /var/lib/machines/fedora-rawhide/sys/fs/selinux (MS_BIND "")...
Remounting /var/lib/machines/fedora-rawhide/sys/fs/selinux (MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_BIND|MS_REMOUNT "")...
Mounting proc on /proc (MS_NOSUID|MS_NOEXEC|MS_NODEV "")...
Bind-mounting /proc/sys on /proc/sys (MS_BIND "")...
Remounting /proc/sys (MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_BIND|MS_REMOUNT "")...
Bind-mounting /proc/sysrq-trigger on /proc/sysrq-trigger (MS_BIND "")...
Remounting /proc/sysrq-trigger (MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_BIND|MS_REMOUNT "")...
Mounting tmpfs on /tmp (MS_STRICTATIME "mode=1777,uid=0,gid=0")...
Mounting tmpfs on /sys/fs/cgroup (MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME "mode=755,uid=0,gid=0")...
Mounting cgroup on /sys/fs/cgroup/systemd (MS_NOSUID|MS_NOEXEC|MS_NODEV "none,name=systemd,xattr")...
Failed to mount cgroup on /sys/fs/cgroup/systemd (MS_NOSUID|MS_NOEXEC|MS_NODEV "none,name=systemd,xattr"): No such file or directory
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.
Despite the name, `Read{Write,Only}Directories=` already allows for
regular file paths to be masked. This commit adds the same behavior
to `InaccessibleDirectories=` and makes it explicit in the doc.
This patch introduces `/run/systemd/inaccessible/{reg,dir,chr,blk,fifo,sock}`
{dile,device}nodes and mounts on the appropriate one the paths specified
in `InacessibleDirectories=`.
Based on Luca's patch from https://github.com/systemd/systemd/pull/3327
Lennart Poettering
Zbigniew Jędrzejewski-Szmek
Yu Watanabe
Timothée Ravier
Alessandro Puccetti
Daniel Mack
Thomas Hindoe Paaboel Andersen