apparmor: fix aa_label_asxprint return check

stable inclusion
from stable-v5.10.138
commit 4188f91c82e3720afd6c65f698ce88c867e02588
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60QFD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4188f91c82e3720afd6c65f698ce88c867e02588



--------------------------------

commit 3e2a3a08 upstream.

Clang static analysis reports this issue
label.c:1802:3: warning: 2nd function call argument
  is an uninitialized value
  pr_info("%s", str);
  ^~~~~~~~~~~~~~~~~~

str is set from a successful call to aa_label_asxprint(&str, ...)
On failure a negative value is returned, not a -1.  So change
the check.

Fixes: f1bd9041 ("apparmor: add the base fns() for domain labels")
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>