apparmor: fix memory leak in verify_header

commit e38c55d upstream.

The function sets `*ns = NULL` on every call, leaking the namespace
string allocated in previous iterations when multiple profiles are
unpacked. This also breaks namespace consistency checking since *ns
is always NULL when the comparison is made.

Remove the incorrect assignment.
The caller (aa_unpack) initializes *ns to NULL once before the loop,
which is sufficient.

Fixes: dd51c84 ("apparmor: provide base for multiple profiles to be replaced at once")
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>
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: m-pellizzer

security/apparmor/policy_unpack.c

@@ -1142,7 +1142,6 @@ static int verify_header(struct aa_ext *e, int required, const char **ns)
 {
 	int error = -EPROTONOSUPPORT;
 	const char *name = NULL;
-	*ns = NULL;
 
 	/* get the interface version */
 	if (!aa_unpack_u32(e, &e->version, "version")) {