From 2f584bd93d64a75ab11b5a5aa31d0b7145da5a86 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= 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;