selinux: Implementation for inode_copy_up_xattr() hook

When a file is copied up in overlay, we have already created file on
upper/ with right label and there is no need to copy up selinux
label/xattr from lower file to upper file. In fact in case of context
mount, we don't want to copy up label as newly created file got its label
from context= option.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Orabug: 25684456

(backport upstream commit 19472b69d639d58415866bf127d5f9005038c105)

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 08384b887bb0d25be6838d0f58d52be74087e199..c4470b11c21490478f7b096d76abe3bad4f9594c 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3224,6 +3224,21 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
        return 0;
 }
 
+static int selinux_inode_copy_up_xattr(const char *name)
+{
+       /* The copy_up hook above sets the initial context on an inode, but we
+        * don't then want to overwrite it by blindly copying all the lower
+        * xattrs up.  Instead, we have to filter out SELinux-related xattrs.
+        */
+       if (strcmp(name, XATTR_NAME_SELINUX) == 0)
+               return 1; /* Discard */
+       /*
+        * Any other attribute apart from SELINUX is not claimed, supported
+        * by selinux.
+        */
+       return -EOPNOTSUPP;
+}
+
 /* file security operations */
 
 static int selinux_revalidate_file_permission(struct file *file, int mask)
@@ -5943,6 +5958,7 @@ static struct security_operations selinux_ops = {
        .inode_listsecurity =           selinux_inode_listsecurity,
        .inode_getsecid =               selinux_inode_getsecid,
        .inode_copy_up =                selinux_inode_copy_up,
+       .inode_copy_up_xattr =          selinux_inode_copy_up_xattr,
 
        .file_permission =              selinux_file_permission,
        .file_alloc_security =          selinux_file_alloc_security,