Re: BUG: mmapfile/writev spurious zero bytes (x86_64/not i386,bisected, reproducable)

[Linus Torvalds]

On Tue, 17 Jun 2008, Andi Kleen wrote:
> 
> If that fixes anything:
> - The caller is broken because it shouldn't pass a faulting source to copy_to_user()
> - And you broken copy_from_user error reporting which shares the same code

Andi, I'm sorry I cc'd you. You are the author of that crap, but the bug 
seems to be that you never even understood what copy_from_user() is 
supposed to do.

The whole *and*only* reason for copy_to/from_user() existing AT ALL is 
exactly the fact that the source or destination access can fault. 

I don't really see why you continually start arguing about things that are 
OBVIOUSLY BUGGY, as if they weren't buggy. Once somebody has debugged a 
buggy routine, you shouldn't argue against it. 

So here's a hint: next time I claim some code of yours is buggy, either 
just acknowledge the bug, or stay silent. You'll look smarter that way.

			Linus
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