Re: [PATCH] Fix poll() nfds check.

["H. Peter Anvin" <hpa@zytor.com>]

Vadim Lobanov wrote:
> Hi,
> 
> This is a trivial patch to fix the nfds check in the poll system call
> implementation. Namely, OPEN_MAX no longer does anything important in
> the kernel, and checking that nfds is greater than max_fdset AND greater
> than OPEN_MAX therefore just seems wrong.
> 
> This brings up a slightly-tangential question: Why do the nfds checks
> exist in select()/poll()? They're not strictly necessary, since bad
> input will be caught later when we validate all the fds, one by one.
> Furthermore, these checks optimize the handling of error cases (which
> should be uncommon) while pessimizing correct usage of the syscalls
> (which should be more common).
> 

The reason for these is presumably to keep applications which uses 
select() to overflow their fd_sets.  Unfortunately fd_set is defined in 
such a way that it's a static size.

Using ulimit seems like a reasonable compromise for this.

	-hpa