[PATCH] selinux: disable setxattr on mountpoint labeled filesystems

This patch disables the setting of SELinux xattrs on files created in
filesystems labeled via mountpoint labeling (mounted with the context=
option).  selinux_inode_setxattr already prevents explicit setxattr from
userspace on such filesystems, so this provides consistent behavior for
file creation.
Signed-off-by: NStephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: NJames Morris <jmorris@namei.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

security/selinux/hooks.c

@@ -1986,6 +1986,9 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 
 	inode_security_set_sid(inode, newsid);
 
+	if (sbsec->behavior == SECURITY_FS_USE_MNTPOINT)
+		return -EOPNOTSUPP;
+
 	if (name) {
 		namep = kstrdup(XATTR_SELINUX_SUFFIX, GFP_KERNEL);
 		if (!namep)