systemd/0438-basic-virt-try-the-proc-1-sched-hack-also-for-PID1.patch

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