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core: let selinux_setup() load policy more than once

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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.
This commit is contained in:
Will Woods 2014-04-25 18:26:34 -04:00 committed by Lennart Poettering
parent d36d90933a
commit 68d3acaccb
Notes: Lennart Poettering 2014-05-19 01:58:57 +09:00 
Backport: bugfix
1 changed files with 7 additions and 7 deletions
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14
src/core/selinux-setup.c
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@ -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
@ -116,8 +112,12 @@ int selinux_setup(bool *loaded_policy) {
log_open();
if (enforce > 0) {
log_error("Failed to load SELinux policy. Freezing.");
return -EIO;
if (!initialized) {
log_error("Failed to load SELinux policy. Freezing.");
return -EIO;
}
log_warning("Failed to load new SELinux policy. Continuing with old policy.");
} else
log_debug("Unable to load SELinux policy. Ignoring.");
}