security: check for kstrdup() failure in lsm_append()

security: check for kstrdup() failure in lsm_append()

BugLink: https://bugs.launchpad.net/bugs/1836117
[ Upstream commit 87ea58433208d17295e200d56be5e2a4fe4ce7d6 ]

lsm_append() should return -ENOMEM if memory allocation failed.

Fixes: d69dece5f5b6 ("LSM: Add /sys/kernel/security/lsm")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: James Morris <james.morris@microsoft.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>