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virt: when detecting containers and /run/systemd/container cannot be read, check /proc/1/environ

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This way, we should be in a slightly better situation if a container is
booted up with only a shell as PID 1. In that case
/run/systemd/container will not be populated, and a check for it hence
be ineffective.

Checking /proc/1/environ doesn't fully fix the problem though, as the
file is only accessible with privileges. This means if PID 1 is not
systemd, and if privileges have been dropped the container detection
will continue to fail.
This commit is contained in:
Lennart Poettering 2014-12-10 13:23:49 +01:00
parent a644abed54
commit 536bfdab4c
1 changed files with 20 additions and 2 deletions
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22
src/shared/virt.c
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@ -293,8 +293,26 @@ int detect_container(const char **id) {
r = read_one_line_file("/run/systemd/container", &m);
if (r == -ENOENT) {
r = 0;
goto finish;
/* Fallback for cases where PID 1 was not
* systemd (for example, cases where
* init=/bin/sh is used. */
r = getenv_for_pid(1, "container", &m);
if (r <= 0) {
/* If that didn't work, give up,
* assume no container manager.
*
* Note: This means we still cannot
* detect containers if init=/bin/sh
* is passed but privileges dropped,
* as /proc/1/environ is only readable
* with privileges. */
r = 0;
goto finish;
}
}
if (r < 0)
return r;