apparmor: Fix double free of ns_name in aa_replace_profiles()

commit 5df0c44e8f5f619d3beb871207aded7c78414502 upstream.

if ns_name is NULL after
1071         error = aa_unpack(udata, &lh, &ns_name);

and if ent->ns_name contains an ns_name in
1089                 } else if (ent->ns_name) {

then ns_name is assigned the ent->ns_name
1095                         ns_name = ent->ns_name;

however ent->ns_name is freed at
1262                 aa_load_ent_free(ent);

and then again when freeing ns_name at
1270         kfree(ns_name);

Fix this by NULLing out ent->ns_name after it is transferred to ns_name

BUG=None
TEST=presubmit
RELEASE_NOTE=Fixed the "CrackArmor" vulnerability in the Linux kernel.

cos-patch: security-high
Fixes: 145a0ef21c8e9 ("apparmor: fix blob compression when ns is forced on a policy load")
Reported-by: Qualys Security Advisory <qsa@qualys.com>
Tested-by: Salvatore Bonaccorso <carnil@debian.org>
Reviewed-by: Georgia Garcia <georgia.garcia@canonical.com>
Reviewed-by: Cengiz Can <cengiz.can@canonical.com>
Change-Id: I78eeec0a5a0ea22cf6a363dd806a9c273631dfff
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 86feeccd6b93ed94bd6655f30de80f163f8d5a45)
Signed-off-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/137847
Reviewed-by: He Gao <hegao@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>