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authorLennart Poettering <lennart@poettering.net>2014-05-28 18:37:11 +0800
committerLennart Poettering <lennart@poettering.net>2014-05-28 18:53:44 +0800
commitfdd25311706bd32580ec4d43211cdf4665d2f9de (patch)
tree37f3d1859779e00321ac69882b40723d5c875531 /src/shared
parentd2edfae0f9bdbecf6a8518e2a5bcf06f470e0d9e (diff)
virt: rework container detection logic
Instead of accessing /proc/1/environ directly, trying to read the $container variable from it, let's make PID 1 save the contents of that variable to /run/systemd/container. This allows us to detect containers without the need for CAP_SYS_PTRACE, which allows us to drop it from a number of daemons and from the file capabilities of systemd-detect-virt. Also, don't consider chroot a container technology anymore. After all, we don't consider file system namespaces container technology anymore, and hence chroot() should be considered a container even less.
Diffstat (limited to 'src/shared')
-rw-r--r--src/shared/virt.c48
1 files changed, 30 insertions, 18 deletions
diff --git a/src/shared/virt.c b/src/shared/virt.c
index 0db0514dd3..1e227c5fbd 100644
--- a/src/shared/virt.c
+++ b/src/shared/virt.c
@@ -217,8 +217,8 @@ int detect_container(const char **id) {
static thread_local int cached_found = -1;
static thread_local const char *cached_id = NULL;
- _cleanup_free_ char *e = NULL;
- const char *_id = NULL;
+ _cleanup_free_ char *m = NULL;
+ const char *_id = NULL, *e = NULL;
int r;
if (_likely_(cached_found >= 0)) {
@@ -229,17 +229,6 @@ int detect_container(const char **id) {
return cached_found;
}
- /* Unfortunately many of these operations require root access
- * in one way or another */
-
- r = running_in_chroot();
- if (r < 0)
- return r;
- if (r > 0) {
- _id = "chroot";
- goto finish;
- }
-
/* /proc/vz exists in container and outside of the container,
* /proc/bc only outside of the container. */
if (access("/proc/vz", F_OK) >= 0 &&
@@ -249,11 +238,32 @@ int detect_container(const char **id) {
goto finish;
}
- r = getenv_for_pid(1, "container", &e);
- if (r < 0)
- return r;
- if (r == 0)
- goto finish;
+ if (getpid() == 1) {
+ /* If we are PID 1 we can just check our own
+ * environment variable */
+
+ e = getenv("container");
+ if (isempty(e)) {
+ r = 0;
+ goto finish;
+ }
+ } else {
+
+ /* Otherwise, PID 1 dropped this information into a
+ * file in /run. This is better than accessing
+ * /proc/1/environ, since we don't need CAP_SYS_PTRACE
+ * for that. */
+
+ r = read_one_line_file("/run/systemd/container", &m);
+ if (r == -ENOENT) {
+ r = 0;
+ goto finish;
+ }
+ if (r < 0)
+ return r;
+
+ e = m;
+ }
/* We only recognize a selected few here, since we want to
* enforce a redacted namespace */
@@ -266,6 +276,8 @@ int detect_container(const char **id) {
else
_id = "other";
+ r = 1;
+
finish:
cached_found = r;