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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
in a strange situation when detect-virt returns container-other when
run as non-pid-1 and none when run as pid-1.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2019-04-26 13:37:31 +02:00
parent a6d04b1a17
commit 342bed0208
1 changed files with 11 additions and 5 deletions
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16
src/basic/virt.c
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@@ -428,7 +428,6 @@ finish:
}
int detect_container(void) {
static const struct {
const char *value;
int id;
@@ -468,9 +467,15 @@ 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;
@@ -498,8 +503,9 @@ 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;