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From 2f584bd93d64a75ab11b5a5aa31d0b7145da5a86 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
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Date: Fri, 26 Apr 2019 13:37:31 +0200
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Subject: [PATCH] basic/virt: try the /proc/1/sched hack also for PID1
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If a container manager does not set $container, we could end up
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in a strange situation when detect-virt returns container-other when
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run as non-pid-1 and none when run as pid-1.
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(cherry picked from commit 342bed02084c4396dd2f1054bd559bfb2699cfcb)
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Resolves: #1868877
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---
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src/basic/virt.c | 16 +++++++++++-----
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1 file changed, 11 insertions(+), 5 deletions(-)
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diff --git a/src/basic/virt.c b/src/basic/virt.c
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index e05b3e6d99..dfa1525219 100644
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--- a/src/basic/virt.c
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+++ b/src/basic/virt.c
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@@ -427,7 +427,6 @@ finish:
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}
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int detect_container(void) {
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-
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static const struct {
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const char *value;
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int id;
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@@ -456,9 +455,15 @@ int detect_container(void) {
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}
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if (getpid_cached() == 1) {
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- /* If we are PID 1 we can just check our own environment variable, and that's authoritative. */
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-
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+ /* If we are PID 1 we can just check our own environment variable, and that's authoritative.
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+ * We distinguish three cases:
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+ * - the variable is not defined → we jump to other checks
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+ * - the variable is defined to an empty value → we are not in a container
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+ * - anything else → some container, either one of the known ones or "container-other"
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+ */
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e = getenv("container");
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+ if (!e)
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+ goto check_sched;
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if (isempty(e)) {
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r = VIRTUALIZATION_NONE;
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goto finish;
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@@ -486,8 +491,9 @@ int detect_container(void) {
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if (r < 0) /* This only works if we have CAP_SYS_PTRACE, hence let's better ignore failures here */
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log_debug_errno(r, "Failed to read $container of PID 1, ignoring: %m");
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- /* Interestingly /proc/1/sched actually shows the host's PID for what we see as PID 1. Hence, if the PID shown
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- * there is not 1, we know we are in a PID namespace. and hence a container. */
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+ /* Interestingly /proc/1/sched actually shows the host's PID for what we see as PID 1. If the PID
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+ * shown there is not 1, we know we are in a PID namespace and hence a container. */
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+ check_sched:
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r = read_one_line_file("/proc/1/sched", &m);
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if (r >= 0) {
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const char *t;
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