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Don't mount /dev/ inside privileged containers running systemd #15895

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dcermak
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@dcermak dcermak commented Sep 21, 2022

According to https://systemd.io/CONTAINER_INTERFACE/, systemd will try take control over /dev/tty if exported, which can cause conflicts with the host's tty in privileged containers. Thus we will not expose these to privileged containers in systemd mode, as this is a bad idea according to systemd's maintainers.

This fixes #15878

Does this PR introduce a user-facing change?

- don't expose `/dev/tty*` to privileged containers in systemd mode

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rhatdan commented Sep 22, 2022

Please repush your PR. I added [NO NEW TESTS NEEDED]
/approve
LGTM
@giuseppe PTAL

@openshift-ci openshift-ci bot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Sep 22, 2022
@dcermak dcermak force-pushed the don-expose-dev-for-privileged branch 3 times, most recently from 78d0925 to af24c04 Compare September 22, 2022 11:42
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dcermak commented Sep 22, 2022

Please repush your PR. I added [NO NEW TESTS NEEDED]

I have removed that and added a bats test, because my initial fix was actually broken (it got late yesterday…).

@dcermak dcermak force-pushed the don-expose-dev-for-privileged branch 2 times, most recently from 67db995 to cefd583 Compare September 22, 2022 14:10
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Please squash your commits - no need for separate code + test commits. And please update your commit message to reflect the new state of the code. A few test suggestions inline.

Thank you, and thanks for contributing!

test/system/030-run.bats Outdated Show resolved Hide resolved
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According to https://systemd.io/CONTAINER_INTERFACE/, systemd will try take
control over /dev/ttyN if exported, which can cause conflicts with the host's tty
in privileged containers. Thus we will not expose these to privileged containers
in systemd mode, as this is a bad idea according to systemd's maintainers.

Additionally, this commit adds a bats regression test to check that no /dev/ttyN
are present in a privileged container in systemd mode

This fixes containers#15878

Signed-off-by: Dan Čermák <[email protected]>
@dcermak dcermak force-pushed the don-expose-dev-for-privileged branch from cefd583 to 5a2405a Compare September 22, 2022 14:47
@dcermak dcermak requested a review from edsantiago September 22, 2022 14:47
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dcermak commented Sep 22, 2022

@edsantiago Thanks for the review, I've squashed the commits and applied your suggested changes.


if [[ $TTYs = "" ]]; then
die "Did not find any /dev/ttyN devices on local host"
else
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It's a little bit confusing to use else after die, since by definition die terminates execution... but not worth re-pushing for, especially given our flaky CI today. I'll fix it in one of my periodic cleanup PRs.

LGTM, but I'll let other more systemd-savvy team members give final approval. Thanks again!

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mheon commented Sep 22, 2022

/lgtm
/approve

@openshift-ci openshift-ci bot added the lgtm Indicates that a PR is ready to be merged. label Sep 22, 2022
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openshift-ci bot commented Sep 22, 2022

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dcermak, edsantiago, mheon, rhatdan

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:
  • OWNERS [edsantiago,mheon,rhatdan]

Approvers can indicate their approval by writing /approve in a comment
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@openshift-merge-robot openshift-merge-robot merged commit 0899351 into containers:main Sep 22, 2022
edsantiago added a commit to edsantiago/libpod that referenced this pull request Sep 27, 2022
Followup to containers#15895:
 - add a normal-case test, to ensure that --privileged without
   systemd continues to pass through /dev/ttyN devices
 - explain why we die() if host has no ttyN devices
 - I find grep -vx slightly easier to read than sed backslash-slash
 - run cleanup with '-t 0', to shave ten seconds from CI run

Signed-off-by: Ed Santiago <[email protected]>
@dcermak dcermak deleted the don-expose-dev-for-privileged branch January 24, 2023 07:38
@github-actions github-actions bot added the locked - please file new issue/PR Assist humans wanting to comment on an old issue or PR with locked comments. label Sep 14, 2023
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podman exposes /dev/tty* to privileged containers when run as root
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