selinux: allow reading labels before policy is loaded

This patch does for `getxattr` what commit 3e3e24b42043 ("selinux: allow
labeling before policy is loaded") did for `setxattr`; it allows
querying the current SELinux label on disk before the policy is loaded.

One of the motivations described in that commit message also drives this
patch: for Fedora CoreOS (and eventually RHEL CoreOS), we want to be
able to move the root filesystem for example, from xfs to ext4 on RAID,
on first boot, at initrd time.[1]

Because such an operation works at the filesystem level, we need to be
able to read the SELinux labels first from the original root, and apply
them to the files of the new root. The previous commit enabled the
second part of this process; this commit enables the first part.

[1] https://github.com/coreos/fedora-coreos-tracker/issues/94

Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
Signed-off-by: Jonathan Lebon <jlebon@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index efa6108b1ce91cf57ea05ff0eff3525ccfd75d43..ca901025802a9e0aa5d5709f90bda8ee283aaa02 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3332,7 +3332,12 @@ static int selinux_inode_getsecurity(struct inode *inode, const char *name, void
        char *context = NULL;
        struct inode_security_struct *isec;
 
-       if (strcmp(name, XATTR_SELINUX_SUFFIX))
+       /*
+        * If we're not initialized yet, then we can't validate contexts, so
+        * just let vfs_getxattr fall back to using the on-disk xattr.
+        */
+       if (!selinux_initialized(&selinux_state) ||
+           strcmp(name, XATTR_SELINUX_SUFFIX))
                return -EOPNOTSUPP;
 
        /*