The original reasoning for this option was to avoid having mount options
be overwritten by runc. However, adding command-line arguments has
historically been a bad idea because it forces strict-runc-compatible
OCI runtimes to copy out-of-spec features directly from runc and these
flags are usually quite difficult to enable by users when using runc
through several layers of engines and orchestrators.
A far more preferable solution is to have a heuristic which detects
whether copying the original mount's mount options would override an
explicit mount option specified by the user. In this case, we should
return an error. You only end up in this path in the userns case, if you
have a bind-mount source with locked flags.
During the course of writing this patch, I discovered that several
aspects of our handling of flags for bind-mounts left much to be
desired. We have completely botched the handling of explicitly cleared
flags since commit 97f5ee4e6a ("Only remount if requested flags differ
from current"), with our behaviour only becoming increasingly more weird
with 50105de1d8 ("Fix failure with rw bind mount of a ro fuse") and
da780e4d27 ("Fix bind mounts of filesystems with certain options
set"). In short, we would only clear flags explicitly request by the
user purely by chance, in ways that it really should've been reported to
us by now. The most egregious is that mounts explicitly marked "rw" were
actually mounted "ro" if the bind-mount source was "ro" and no other
special flags were included. In addition, our handling of atime was
completely broken -- mostly due to how subtle the semantics of atime are
on Linux.
Unfortunately, while the runtime-spec requires us to implement
mount(8)'s behaviour, several aspects of the util-linux mount(8)'s
behaviour are broken and thus copying them makes little sense. Since the
runtime-spec behaviour for this case (should mount options for a "bind"
mount use the "mount --bind -o ..." or "mount --bind -o remount,..."
semantics? Is the fallback code we have for userns actually
spec-compliant?) and the mount(8) behaviour (see [1]) are not
well-defined, this commit simply fixes the most obvious aspects of the
behaviour that are broken while keeping the current spirit of the
implementation.
NOTE: The handling of atime in the base case is left for a future PR to
deal with. This means that the atime of the source mount will be
silently left alone unless the fallback path needs to be taken, and any
flags not explicitly set will be cleared in the base case. Whether we
should always be operating as "mount --bind -o remount,..." (where we
default to the original mount source flags) is a topic for a separate PR
and (probably) associated runtime-spec PR.
So, to resolve this:
* We store which flags were explicitly requested to be cleared by the
user, so that we can detect whether the userns fallback path would end
up setting a flag the user explicitly wished to clear. If so, we
return an error because we couldn't fulfil the configuration settings.
* Revert 97f5ee4e6a ("Only remount if requested flags differ from
current"), as missing flags do not mean we can skip MS_REMOUNT (in
fact, missing flags are how you indicate a flag needs to be cleared
with mount(2)). The original purpose of the patch was to fix the
userns issue, but as mentioned above the correct mechanism is to do a
fallback mount that copies the lockable flags from statfs(2).
* Improve handling of atime in the fallback case by:
- Correctly handling the returned flags in statfs(2).
- Implement the MNT_LOCK_ATIME checks in our code to ensure we
produce errors rather than silently producing incorrect atime
mounts.
* Improve the tests so we correctly detect all of these contingencies,
including a general "bind-mount atime handling" test to ensure that
the behaviour described here is accurate.
This change also inlines the remount() function -- it was only ever used
for the bind-mount remount case, and its behaviour is very bind-mount
specific.
[1]: https://github.com/util-linux/util-linux/issues/2433
Reverts: 97f5ee4e6a ("Only remount if requested flags differ from current")
Fixes: 50105de1d8 ("Fix failure with rw bind mount of a ro fuse")
Fixes: da780e4d27 ("Fix bind mounts of filesystems with certain options set")
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Burstable CFS controller is introduced in Linux 5.14. This helps with
parallel workloads that might be bursty. They can get throttled even
when their average utilization is under quota. And they may be latency
sensitive at the same time so that throttling them is undesired.
This feature borrows time now against the future underrun, at the cost
of increased interference against the other system users, by introducing
cfs_burst_us into CFS bandwidth control to enact the cap on unused
bandwidth accumulation, which will then used additionally for burst.
The patch adds the support/control for CFS bandwidth burst.
runtime-spec: https://github.com/opencontainers/runtime-spec/pull/1120
Co-authored-by: Akihiro Suda <suda.kyoto@gmail.com>
Co-authored-by: Nadeshiko Manju <me@manjusaka.me>
Signed-off-by: Kailun Qin <kailun.qin@intel.com>
Currently bind mounts of filesystems with nodev, nosuid, noexec,
noatime, relatime, strictatime, nodiratime options set fail in rootless
mode if the same options are not set for the bind mount.
For ro filesystems this was resolved by #2570 by remounting again
with ro set.
Follow the same approach for nodev, nosuid, noexec, noatime, relatime,
strictatime, nodiratime but allow to revert back to the old behaviour
via the new `--no-mount-fallback` command line option.
Add a testcase to verify that bind mounts of filesystems with nodev,
nosuid, noexec, noatime options set work in rootless mode.
Add a testcase that mounts a nodev, nosuid, noexec, noatime filesystem
with a ro flag.
Add two further testcases that ensure that the above testcases would
fail if the `--no-mount-fallback` command line option is set.
* contrib/completions/bash/runc:
Add `--no-mount-fallback` command line option for bash completion.
* create.go:
Add `--no-mount-fallback` command line option.
* restore.go:
Add `--no-mount-fallback` command line option.
* run.go:
Add `--no-mount-fallback` command line option.
* libcontainer/configs/config.go:
Add `NoMountFallback` field to the `Config` struct to store
the command line option value.
* libcontainer/specconv/spec_linux.go:
Add `NoMountFallback` field to the `CreateOpts` struct to store
the command line option value and store it in the libcontainer
config.
* utils_linux.go:
Store the command line option value in the `CreateOpts` struct.
* libcontainer/rootfs_linux.go:
In case that `--no-mount-fallback` is not set try to remount the
bind filesystem again with the options nodev, nosuid, noexec,
noatime, relatime, strictatime or nodiratime if they are set on
the source filesystem.
* tests/integration/mounts_sshfs.bats:
Add testcases and rework sshfs setup to allow specifying
different mount options depending on the test case.
Signed-off-by: Ruediger Pluem <ruediger.pluem@vodafone.com>
This was introduced in an initial commit, back in the day when criu was
a highly experimental thing. Today it's not; most users who need it have
it packaged by their distro vendor.
The usual way to run a binary is to look it up in directories listed in
$PATH. This is flexible enough and allows for multiple scenarios (custom
binaries, extra binaries, etc.). This is the way criu should be run.
Make --criu a hidden option (thus removing it from help). Remove the
option from man pages, integration tests, etc. Remove all traces of
CriuPath from data structures.
Add a warning that --criu is ignored and will be removed.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Currently, if a container is paused (i.e. its cgroup is frozen), runc exec
just hangs, and it is not obvious why.
Refuse to exec in a paused container. Add a test case.
In case runc exec in a paused container is a legit use case,
add --ignore-paused option to override the check. Document it,
add a test case.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Commit 7a0302f0d7 already removed "runc init" from runc help output,
as this is an internal option not supposed to be used by the end user.
Let's remove runc init completion, too.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This is somewhat radical approach to deal with kernel memory.
Per-cgroup kernel memory limiting was always problematic. A few
examples:
- older kernels had bugs and were even oopsing sometimes (best example
is RHEL7 kernel);
- kernel is unable to reclaim the kernel memory so once the limit is
hit a cgroup is toasted;
- some kernel memory allocations don't allow failing.
In addition to that,
- users don't have a clue about how to set kernel memory limits
(as the concept is much more complicated than e.g. [user] memory);
- different kernels might have different kernel memory usage,
which is sort of unexpected;
- cgroup v2 do not have a [dedicated] kmem limit knob, and thus
runc silently ignores kernel memory limits for v2;
- kernel v5.4 made cgroup v1 kmem.limit obsoleted (see
https://github.com/torvalds/linux/commit/0158115f702b).
In view of all this, and as the runtime-spec lists memory.kernel
and memory.kernelTCP as OPTIONAL, let's ignore kernel memory
limits (for cgroup v1, same as we're already doing for v2).
This should result in less bugs and better user experience.
The only bad side effect from it might be that stat can show kernel
memory usage as 0 (since the accounting is not enabled).
[v2: add a warning in specconv that limits are ignored]
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This allows a user to send a signal to all the processes in the
container within a single atomic action to avoid new processes being
forked off before the signal can be sent.
This is basically taking functionality that we already use being
`delete` and exposing it ok the `kill` command by adding a flag.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Daniel Levi-Minzi