ima: Simplify ima_lsm_copy_rule

maillist inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I61O87
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=d57378d3aa4d864d9e590482602068af1b20c0c5



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

Currently ima_lsm_copy_rule() set the arg_p field of the source rule to
NULL, so that the source rule could be freed afterward. It does not make
sense for this behavior to be inside a "copy" function. So move it
outside and let the caller handle this field.

ima_lsm_copy_rule() now produce a shallow copy of the original entry
including args_p field. Meaning only the lsm.rule and the rule itself
should be freed for the original rule. Thus, instead of calling
ima_lsm_free_rule() which frees lsm.rule as well as args_p field, free
the lsm.rule directly.

Signed-off-by: GUO Zihua <guozihua@huawei.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Conflicts:
	security/integrity/ima/ima_policy.c
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: GUO Zihua <guozihua@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>