[PATCH v2] selinux: bpf: check SBLABEL_MNT before isec init

selinux_inode_init_security() marks the isec as initialized before
checking if mount labeling is supported (SBLABEL_MNT). This was fine
until commit 9722955b5430 ("bpf: Add simple xattr support to bpffs"),
where genfscon bpffs mounts fail the SBLABEL_MNT check as expected (no
xattrs) and yet leave the isec->initialized. This breaks subsequent
calls to inode_doinit_with_dentry().

Do the SBLABEL_MNT check before the inode security is initialized.

Cc: [email protected]
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 9722955b5430 ("bpf: Add simple xattr support to bpffs")
Acked-by: Stephen Smalley <[email protected]>
Signed-off-by: Carlos Llamas <[email protected]>
---
v2:
  - Move the check further at the top per Paul's feedback.
  - Collect Stephen's Ack.

v1:
  https://lore.kernel.org/all/[email protected]/

 security/selinux/hooks.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 8d6945edae7a..18dd28b2bb13 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2974,6 +2974,10 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 
 	sbsec = selinux_superblock(dir->i_sb);
 
+	if (!selinux_initialized() ||
+	    !(sbsec->flags & SBLABEL_MNT))
+		return -EOPNOTSUPP;
+
 	newsid = crsec->create_sid;
 	newsclass = inode_mode_to_security_class(inode->i_mode);
 	rc = selinux_determine_inode_label(crsec, dir, qstr, newsclass, &newsid);
@@ -2988,10 +2992,6 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 		isec->initialized = LABEL_INITIALIZED;
 	}
 
-	if (!selinux_initialized() ||
-	    !(sbsec->flags & SBLABEL_MNT))
-		return -EOPNOTSUPP;
-
 	xattr = lsm_get_xattr_slot(xattrs, xattr_count);
 	if (xattr) {
 		rc = security_sid_to_context_force(newsid,
-- 
2.55.0.508.g3f0d502094-goog