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virt: revert to detect chroot by comparing with / rather than /proc/PID/root

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This partially reverts d6267b9b18

So, arch-chroot currently uses a rather cursed setup:
it sets up a PID namespace, but mounts /proc/ from the outside
into the chroot tree, and then call chroot(2), essentially
making it somewhere between chroot(8) and a full-blown
container. Hence, the PID dirs in /proc/ reveal the outer world.
The offending commit switched chroot detection to compare
/proc/1/root and /proc/OUR_PID/root, exhibiting the faulty behavior
where the mentioned environment now gets deemed to be non-chroot.

Now, this is very much an issue in arch-chroot. However,
if /proc/ is to be properly associated with the pidns,
then we'd treat it as a container and no longer a chroot.
Also, the previous logic feels more readable and more
honestly reported errors in proc_mounted(). Hence I opted
for reverting the change here. Still note that the culprit
(once again :/) lies in the arch-chroot's pidns impl, not
systemd.

Fixes https://gitlab.archlinux.org/archlinux/packaging/packages/systemd/-/issues/54
This commit is contained in:
Mike Yuan
2025-09-19 01:16:19 +02:00
committed by Lennart Poettering
parent c3c42b30dd
commit 01184496a2
1 changed files with 12 additions and 9 deletions
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21
src/basic/virt.c
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@@ -16,8 +16,8 @@
#include "log.h"
#include "namespace-util.h"
#include "parse-util.h"
#include "pidref.h"
#include "process-util.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
@@ -816,16 +816,19 @@ int running_in_chroot(void) {
if (getenv_bool("SYSTEMD_IGNORE_CHROOT") > 0)
return 0;
r = pidref_from_same_root_fs(&PIDREF_MAKE_FROM_PID(1), NULL);
if (r == -ENOSYS) {
if (getpid_cached() == 1)
return false; /* We will mount /proc, assuming we're not in a chroot. */
r = inode_same("/proc/1/root", "/", /* flags = */ 0);
if (r == -ENOENT) {
r = proc_mounted();
if (r == 0) {
if (getpid_cached() == 1)
return false; /* We will mount /proc, assuming we're not in a chroot. */
log_debug("/proc/ is not mounted, assuming we're in a chroot.");
return true;
log_debug("/proc/ is not mounted, assuming we're in a chroot.");
return true;
}
if (r > 0) /* If we have fake /proc/, we can't do the check properly. */
return -ENOSYS;
}
if (r == -ESRCH) /* We must have a fake /proc/, we can't do the check properly. */
return -ENOSYS;
if (r < 0)
return r;