Re: [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush_pending

On Thu, Jan 7, 2021 at 2:31 PM Andrea Arcangeli [off-list ref] wrote:

Random memory corruption will still silently materialize as result of
the speculative lookups in the above scenario.

Explain.

Yes, you'll get random memory corruption if you keep doing wrprotect()
without mmap_sem held for writing.

But I thought we agreed earlier that that is a bug. And I thought the
softdirty code already got it for writing.

           Linus