Yes, the case is that we would like to filter out the "thread creation" and only keep the "process creation", by excluding the CLONE_THREAD flag bit of a0 of clone() syscall.
Without the audit comparator support for this case, we have to filter out the "thread creation" in user space which introduces a performance penalty.
Regards,
Richard
Hello,
On Wednesday, March 8, 2023 8:46:57 AM EST Richard Du wrote:
> I'm trying to define an audit rule with auditctl for clone() syscall, and I
> would expect that the a0 of clone() syscall (i.e. the clone_flags
> argument) without the CLONE_THREAD flag bit being set.
>
> int clone(int (*fn)(void *), void *stack, int flags, void *arg, ...
> /* pid_t *parent_tid, void *tls, pid_t *child_tid */ );
>
> From man page of auditctl, -F option build a rule file: name, operation,
> value.
> -F [n=v | n!=v | n<v | n>v | n<=v | n>=v | n&v | n&=v]
>
> I can understand that, the n&v (Audit_bitmask) means any bit of a bitmast
> is set, and the n&=v (Audit_bittest) means all bits of a bitmask are set.
>
> While my question is, how to build a rule which means "none of bit of a
> bitmask is set", i.e. ( ! n&=v ). If the current audit comparator dosen't
> support this, can we add the support in furture?
The comparator does not support this. This is a corner case in which this is
the first time someone ever needed it.
-Steve