How to define audit rule for one bit *not* set for a syscall argument?

[Steve Grubb]

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