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logind: chown+chmod /run/user/$UID if mount(tmpfs) fails with EPERM

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In containers without CAP_SYS_ADMIN, it is not possible to mount tmpfs
(or any filesystem for that matter) on top of /run/user/$UID.
Previously, logind just failed in such a situation.

Now, logind will resort to chown+chmod of the directory instead. This
allows logind still to work in those environments, although without the
guarantees it provides (i.e. users not being able to DOS /run or other
users' /run/user/$UID space) when CAP_SYS_ADMIN is available.
This commit is contained in:
Christian Seiler 2015-01-27 18:58:40 +01:00 committed by Lennart Poettering
parent 4d858e7d9f
commit 11c6476a08
1 changed files with 19 additions and 3 deletions
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22
src/login/logind-user.c
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@ -335,8 +335,20 @@ static int user_mkdir_runtime_path(User *u) {
r = mount("tmpfs", p, "tmpfs", MS_NODEV|MS_NOSUID, t);
if (r < 0) {
r = log_error_errno(errno, "Failed to mount per-user tmpfs directory %s: %m", p);
goto fail;
if (errno != EPERM) {
r = log_error_errno(errno, "Failed to mount per-user tmpfs directory %s: %m", p);
goto fail;
}
/* Lacking permissions, maybe
* CAP_SYS_ADMIN-less container? In this case,
* just use a normal directory. */
r = chmod_and_chown(p, 0700, u->uid, u->gid);
if (r < 0) {
log_error_errno(r, "Failed to change runtime directory ownership and mode: %m");
goto fail;
}
}
}
@ -514,7 +526,11 @@ static int user_remove_runtime_path(User *u) {
if (r < 0)
log_error_errno(r, "Failed to remove runtime directory %s: %m", u->runtime_path);
if (umount2(u->runtime_path, MNT_DETACH) < 0)
/* Ignore cases where the directory isn't mounted, as that's
* quite possible, if we lacked the permissions to mount
* something */
r = umount2(u->runtime_path, MNT_DETACH);
if (r < 0 && errno != EINVAL && errno != ENOENT)
log_error_errno(errno, "Failed to unmount user runtime directory %s: %m", u->runtime_path);
r = rm_rf(u->runtime_path, false, true, false);