Re: [PATCH v2 12/32] mm/vmalloc: vmalloc_to_page() use pte_offset_kernel()

Will Deacon
2023-07-20T10:33:51Z

On Tue, Jul 11, 2023 at 06:57:33PM +0100, Mark Brown wrote:
> On Tue, Jul 11, 2023 at 09:13:18AM -0700, Hugh Dickins wrote:
> > On Tue, 11 Jul 2023, Mark Brown wrote:
> > > On Mon, Jul 10, 2023 at 09:34:42PM -0700, Hugh Dickins wrote:
> > >
> > > > I suppose I should ask you to try reverting this 0d1c81edc61e alone
> > > > from 6.5-rc1: the consistency of your bisection implies that it will
> > > > "fix" the issues, and it is a commit which we could drop. It makes
> > > > me a little nervous, applying userspace-pagetable validation to kernel
> > > > pagetables, so I don't want to drop it; and it would really be cargo-
> > > > culting to drop it without understanding. But we could drop it.
> > >
> > > I did look at that, it doesn't revert cleanly by itself. ...
> >
> > Right, that ptep_get() wrapper on the next line came in on top.
> > The patch to revert just 0d1c81edc61e is this:
>
> Still investigating but I'm pretty convinced this is nothing to do with
> your commit/series and is just common or garden memory corruption that
> just happens to get tickled by your changes. Sorry for the noise.

Did you get to the bottom of this? If not, do you have a reliable way to
reproduce the problem? I don't like the sound of memory corruption :(

Will