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From c043ae5b2ef2e1e437bf738bbf522799c6213230 Mon Sep 17 00:00:00 2001
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From: Krzysztof Nowicki <krzysztof.a.nowicki+github@gmail.com>
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Date: Thu, 30 Nov 2017 11:59:29 +0100
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Subject: [PATCH] Fix SELinux labels in cgroup filesystem root directory
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(#7496)
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When using SELinux with legacy cgroups the tmpfs on /sys/fs/cgroup is by
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default labelled as tmpfs_t. This label is also inherited by the "cpu"
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and "cpuacct" symbolic links. Unfortunately the policy expects them to
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be labelled as cgroup_t, which is used for all the actual cgroup
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filesystems. Failure to do so results in a stream of denials.
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This state cannot be fixed reliably when the cgroup filesystem structure
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is set-up as the SELinux policy is not yet loaded at this
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moment. It also cannot be fixed later as the root of the cgroup
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filesystem is remounted read-only. In order to fix it the root of the
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cgroup filesystem needs to be temporary remounted read-write, relabelled
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and remounted back read-only.
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(cherry picked from commit 8739f23e3c26bbf8b0296421578e56daa63cbf4b)
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---
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src/core/mount-setup.c | 10 +++++++++-
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1 file changed, 9 insertions(+), 1 deletion(-)
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diff --git a/src/core/mount-setup.c b/src/core/mount-setup.c
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index 521545e5c..7a2cae4a3 100644
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--- a/src/core/mount-setup.c
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+++ b/src/core/mount-setup.c
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@@ -363,14 +363,22 @@ int mount_setup(bool loaded_policy) {
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usec_t before_relabel, after_relabel;
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char timespan[FORMAT_TIMESPAN_MAX];
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+ mkdir_label("/run/systemd/policy-relabelling", 0755);
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before_relabel = now(CLOCK_MONOTONIC);
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nftw("/dev", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
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nftw("/run", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
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+ /* Temporarily remount the root cgroup filesystem to give it a proper label. */
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+ (void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT, NULL);
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+ label_fix("/sys/fs/cgroup", false, false);
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+ nftw("/sys/fs/cgroup", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
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+ (void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT|MS_RDONLY, NULL);
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+
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after_relabel = now(CLOCK_MONOTONIC);
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- log_info("Relabelled /dev and /run in %s.",
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+ mkdir_label("/run/systemd/policy-relabelled", 0755);
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+ log_info("Relabelled /dev, /run and /sys/fs/cgroup in %s.",
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format_timespan(timespan, sizeof(timespan), after_relabel - before_relabel, 0));
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}
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#endif
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