[PATCH 5.2 180/215] selinux: check sidtab limit before adding a new entry

[Greg Kroah-Hartman]

From: Ondrej Mosnacek <omosn...@redhat.com>

commit acbc372e6109c803cbee4733769d02008381740f upstream.

We need to error out when trying to add an entry above SIDTAB_MAX in
sidtab_reverse_lookup() to avoid overflow on the odd chance that this
happens.

Cc: sta...@vger.kernel.org
Fixes: ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve 
performance")
Signed-off-by: Ondrej Mosnacek <omosn...@redhat.com>
Reviewed-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: Paul Moore <p...@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 security/selinux/ss/sidtab.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/security/selinux/ss/sidtab.c
+++ b/security/selinux/ss/sidtab.c
@@ -286,6 +286,11 @@ static int sidtab_reverse_lookup(struct
                ++count;
        }
 
+       /* bail out if we already reached max entries */
+       rc = -EOVERFLOW;
+       if (count >= SIDTAB_MAX)
+               goto out_unlock;
+
        /* insert context into new entry */
        rc = -ENOMEM;
        dst = sidtab_do_lookup(s, count, 1);