CVE-2011-4110 kernel: keys: NULL pointer deref in the user-defined key type

[Petr Matousek <pmatouse () redhat com>]

There is a NULL pointer deref in the user-defined key type whereby
updating a negative key into a fully instantiated key will cause
an oops to occur when the code attempts to free the non-existent
old payload.

Upstream commit:
9f35a33b8d06263a165efe3541d9aa0cdbd70b3b

References:
https://lkml.org/lkml/2011/11/15/363
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2011-4110

Thanks,
-- 
Petr Matousek / Red Hat Security Response Team