Messages in this thread | | | Date | Tue, 9 Aug 2022 22:23:49 +0200 | Subject | Re: [PATCH v1] mm/gup: fix FOLL_FORCE COW security issue and remove FOLL_COW | From | David Hildenbrand <> |
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On 09.08.22 22:20, Linus Torvalds wrote: > On Tue, Aug 9, 2022 at 1:14 PM Linus Torvalds > <torvalds@linux-foundation.org> wrote: >> >> But as there are two bits, I'm sure somebody ends up touching one and >> not the other. > > Ugh. The nommu code certainly does odd things here. That just looks wrong. > > And the hugetlb code does something horrible too, but never *sets* it, > so it looks like some odd subset of VM_SHARED.
mm/mmap.c:do_mmap() contains the magic bit
switch (flags & MAP_TYPE) { case MAP_SHARED: ... case MAP_SHARED_VALIDATE: ... vm_flags |= VM_SHARED | VM_MAYSHARE; if (!(file->f_mode & FMODE_WRITE)) vm_flags &= ~(VM_MAYWRITE | VM_SHARED); fallthrough;
VM_SHARED semantics are confusing.
-- Thanks,
David / dhildenb
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