Security: Add Hook to test if the particular xattr is part of a MAC model.

The interface to request security labels from user space is the xattr
interface. When requesting the security label from an NFS server it is
important to make sure the requested xattr actually is a MAC label. This allows
us to make sure that we get the desired semantics from the attribute instead of
something else such as capabilities or a time based LSM.

Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
Signed-off-by: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index b1f7bd727bd9..bbf219a494d0 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5454,6 +5454,11 @@ abort_change:
         return error;
 }
 
+static int selinux_ismaclabel(const char *name)
+{
+        return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0);
+}
+
 static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
         return security_sid_to_context(secid, secdata, seclen);
@@ -5692,6 +5697,7 @@ static struct security_operations selinux_ops = {
         .getprocattr =                  selinux_getprocattr,
         .setprocattr =                  selinux_setprocattr,
 
+        .ismaclabel =                   selinux_ismaclabel,
         .secid_to_secctx =              selinux_secid_to_secctx,
         .secctx_to_secid =              selinux_secctx_to_secid,
         .release_secctx =               selinux_release_secctx,