[Bug 229696] Misplaced negation symbol in auditon(2)'s A_SETPOLICY cmd option

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=229696

            Bug ID: 229696
           Summary: Misplaced negation symbol in auditon(2)'s A_SETPOLICY
                    cmd option
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: aniketp at iitk.ac.in

The system code for auditon(2)'s A_{GET/SET}POLICY command confirms whether
user submitted only the allowed values for A_{SET/GET}POLICY by the following
method:

if (udata.au_policy & ~(AUDIT_CNT|AUDIT_AHLT|AUDIT_ARGV|AUDIT_ARGE))
        return (EINVAL);

That is: If a bit other than the 4 mentioned above is submitted, we'll get
EINVAL.

However, The negation bit is misplaced for "udata.au_policy64" case:

if (udata.au_policy & (~AUDIT_CNT|AUDIT_AHLT|AUDIT_ARGV|AUDIT_ARGE))
        return (EINVAL);

This returns EINVAL almost everytime. The only occasion when I got a success
was passing 0 as the flags, which is not recommended if the system already has
some of the flags set.

TEST PLAN: 
========
Try this piece of code. If your system has any of the flags set, you'll
probably get EINVAL too.

#include <bsm/audit.h>
#include <stdio.h>

void main(){
        int auditpolicy;
        auditon(A_GETPOLICY, &auditpolicy, sizeof(&auditpolicy));
        printf("retrieved policy = %d\n", auditpolicy);

        int retval = auditon(A_SETPOLICY, &auditpolicy, sizeof(&auditpolicy));
        if (retval < 0)
                perror("setpolicy");
}

Fix: review D16222

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