Messages in this thread | | | Date | Mon, 21 Dec 2020 13:03:57 -0500 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] mm/userfaultfd: fix memory corruption due to writeprotect |
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Hello,
On Sat, Dec 19, 2020 at 09:08:55PM -0800, Andy Lutomirski wrote: > On Sat, Dec 19, 2020 at 6:49 PM Andrea Arcangeli <aarcange@redhat.com> wrote: > > The ptes are changed always with the PT lock, in fact there's no > > problem with the PTE updates. The only difference with mprotect > > runtime is that the mmap_lock is taken for reading. And the effect > > contested for this change doesn't affect the PTE, but supposedly the > > tlb flushing deferral. > > Can you point me at where the lock ends up being taken in this path?
pte_offset_map_lock in change_pte_range, as in mprotect, no difference.
As I suspected on my follow up, the bug described wasn't there, but I'll look at the new theory posted.
Thanks, Andrea
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