RE: [PATCH] x86: Allow user accesses to the base of the guard page

[David Laight]

From: Linus Torvalds
> Sent: 23 November 2024 23:45
> 
> On Sat, 23 Nov 2024 at 14:36, David Laight <David.Laight@xxxxxxxxxx> wrote:
> >
> > The problem is that it is valid to pass a buffer that ends right
> > at the end of valid user memory.
> 
> There's a difference between "valid" and "we care".
> 
> This is way past that case. The only possible reason for that
> zero-byte thing at the end of the address space is somebody actively
> looking for some edge case, not a real use.

Mikel gave the exact test that was failing.

I should have been more clear that the issue is fixing valid transfers
that end at the end of valid memory without breaking zero length
transfers anywhere else.

	David

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