Re: [PATCH] fix undefined behavior in ptrace

[Rich Felker <dalias@libc.org>]

On Wed, Jun 28, 2017 at 06:22:12PM +0300, Alexander Monakov wrote:
> On Wed, 28 Jun 2017, Rich Felker wrote:
> > I think there's still UB here, reading more args than were passed.
> > These calls to va_arg should probably be dependent on the particular
> > req; I don't see any reason for it to be compile-time dependent on the
> > presence of one particular req value.
> 
> I raised that last year but there was no response:
> http://www.openwall.com/lists/musl/2016/05/04/18

I'm sorry for overlooking it then. Could you submit a fleshed-out
patch that uses that approach? Assuming the arg types are always the
same, and only the number of args varies by command, a nicer approach
than nested if's with a bunch of equality comparisons each might be a
switch statement to map commands to # of args, then

	if (nargs>=1) pid = va_arg(ap, pid_t);
	if (nargs>=2) addr = va_arg(ap, void *);
	...

Thoughts?

Rich