Re: [PATCH] dup2: Fix return value with oldfd == newfd and invalid fd

[Linus Torvalds <torvalds@linux-foundation.org>]

On Mon, 11 May 2009, Al Viro wrote:
> 
> I'm not sure that it's a right fix, actually.  Note that userland declaration
> of that sucker is int dup2(int, int); so should we really take unsigned int
> as arguments?

Hmm. They've been "unsigned int" for as long as our history goes back 
(including BK), but yes, making them "int" would have hidden this issue as 
well. 

That said, I think we had reasons to do our fd's as unsigned, ie the whole 
"compare against MAX" thing that doesn't take negative values into 
account.

In fact, I think we should do more of those. Right now we literally depend 
on things like "max_fds" being "unsigned int", and that the compiler then 
turns all the

	if (fd < fdt->max_fds)

tests silently into unsigned tests even when 'fd' is 'int'.

So I suspect we should probably make fs/file.c use _more_ "unsigned int" 
rather than having less of them.

			Linus