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SubjectRe: [PATCH 1/1] mm: fix use-after-free bug when mm->mmap is reused after being freed
On Thu 24-02-22 20:18:59, Andrew Morton wrote:
> On Tue, 15 Feb 2022 12:19:22 -0800 Suren Baghdasaryan <surenb@google.com> wrote:
>
> > After exit_mmap frees all vmas in the mm, mm->mmap needs to be reset,
> > otherwise it points to a vma that was freed and when reused leads to
> > a use-after-free bug.
> >
> > ...
> >
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -3186,6 +3186,7 @@ void exit_mmap(struct mm_struct *mm)
> > vma = remove_vma(vma);
> > cond_resched();
> > }
> > + mm->mmap = NULL;
> > mmap_write_unlock(mm);
> > vm_unacct_memory(nr_accounted);
> > }
>
> After the Maple tree patches, mm_struct.mmap doesn't exist. So I'll
> revert this fix as part of merging the maple-tree parts of linux-next.
> I'll be sending this fix to Linus this week.

But this is a regression introduced in this release cycle so the patch
should be merged before Maple tree patches, no?
--
Michal Hocko
SUSE Labs

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