Re: [PATCH] Fix compat regression in process_vm_rw()

[Linus Torvalds]

On Tue, Oct 27, 2020 at 1:01 AM Christoph Hellwig <hch@xxxxxx> wrote:
>
> Independent of this fix I think we just need to explicitly prohibit
> cross-access.

Well, prohibiting a 32-bit process from accessing a 64-bit one might
make sense, since it fundamentally cannot work, and returning an
explicit error early might help avoid confusion.

But a 64-bit one can certainly validly look at a 32-bit one (ie
debugging a compat process from a 64-bit gdb or similar is not
unreasonable).

That said, I wonder how muich of a problem that can be, so it may be
sufficient to just fix this compat case up and leave it alone.

So applied,

            Linus