When you switch-root into a new root that has SELinux policy, you're
supposed to to run selinux_init_load_policy() to set up SELinux and load
policy. Normally this gets handled by selinux_setup().
But if SELinux was already initialized, selinux_setup() skips loading
policy and returns 0. So if you load policy normally, and then you
switch-root to a new root that has new policy, selinux_setup() never
loads the new policy. What gives?
As far as I can tell, this check is an artifact of how selinux_setup()
worked when it was first written (see commit c4dcdb9 / systemd v12):
* when systemd starts, run selinux_setup()
* if selinux_setup() loads policy OK, restart systemd
So the "if policy already loaded, skip load and return 0" check was
there to prevent an infinite re-exec loop.
Modern systemd only calls selinux_setup() on initial load and after
switch-root, and selinux_setup() no longer restarts systemd, so we don't
need that check to guard against the infinite loop anymore.
So: this patch removes the "return 0", thus allowing selinux_setup() to
actually perform SELinux setup after switch-root.
We still want to check to see if SELinux is initialized, because if
selinux_init_load_policy() fails *but* SELinux is initialized that means
we still have (old) policy active. So we don't need to halt if
enforce=1.
---
src/core/selinux-setup.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/src/core/selinux-setup.c b/src/core/selinux-setup.c
index 6d8bc89..578a18f 100644
--- a/src/core/selinux-setup.c
+++ b/src/core/selinux-setup.c
@@ -51,6 +51,7 @@ int selinux_setup(bool *loaded_policy) {
security_context_t con;
int r;
union selinux_callback cb;
+ bool initialized = false;
assert(loaded_policy);
@@ -68,13 +69,8 @@ int selinux_setup(bool *loaded_policy) {
/* Already initialized by somebody else? */
r = getcon_raw(&con);
if (r == 0) {
- bool initialized;
-
initialized = !streq(con, "kernel");
freecon(con);
-
- if (initialized)
- return 0;
}
/* Make sure we have no fds open while loading the policy and
@@ -115,9 +111,11 @@ int selinux_setup(bool *loaded_policy) {
} else {
log_open();
- if (enforce > 0) {
+ if ((enforce > 0) && (!initialized)) {
log_error("Failed to load SELinux policy. Freezing.");
return -EIO;
+ } else if (enforce > 0) {
+ log_warning("Failed to load new SELinux policy.
Continuing with old policy.");
} else
log_debug("Unable to load SELinux policy. Ignoring.");
}
--
1.9.0
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