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

[Al Viro <viro@ZenIV.linux.org.uk>]

On Mon, May 11, 2009 at 11:40:56AM -0700, Linus Torvalds wrote:
> 
> 
> On Mon, 11 May 2009, Jeff Mahoney wrote:
> > 
> >  The return value of dup2 when oldfd == newfd and the fd isn't valid is not
> >  getting properly sign extended. We end up with 4294967287 instead of -EBADF.
> 
> Indeed.
> 
> >  This patch uses a signed int for the error value so it is properly extended.
> 
> However, I'd rather move the new variable into the block where it is used, 
> and keep the whole corner-case thing self-contained.
> 
> So can you verify that this trivial variation on the patch is ok by you, 
> and I'll commit it as yours with your message? (I realize it's really 
> trivial, and I could just do this myself, but good to get the change 
> ack'ed anyway).

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?