selinux: allow reading labels before policy is loaded

This patch does for `getxattr` what commit 3e3e24b420 ("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>
This commit is contained in:
Jonathan Lebon 2020-05-28 10:39:40 -04:00 committed by Paul Moore
parent b3a9e3b962
commit c8e222616c

View File

@ -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;
/*