Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1696559

Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap

From Andrea Arcangeli <aarcange@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap
Date 2017-07-25 23:30 +0200
Message-ID <u7fyX-8aW-65@gated-at.bofh.it> (permalink)
References (5 earlier) <u790v-3Vq-9@gated-at.bofh.it> <u79MR-4rG-3@gated-at.bofh.it> <u79Wx-4x9-5@gated-at.bofh.it> <u7a6f-4Ah-33@gated-at.bofh.it> <u7azf-4ZJ-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Tue, Jul 25, 2017 at 06:04:00PM +0200, Michal Hocko wrote:
> -	down_write(&mm->mmap_sem);
> +	if (tsk_is_oom_victim(current))
> +		down_write(&mm->mmap_sem);
>  	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
>  	tlb_finish_mmu(&tlb, 0, -1);
>  
> @@ -3012,7 +3014,8 @@ void exit_mmap(struct mm_struct *mm)
>  	}
>  	mm->mmap = NULL;
>  	vm_unacct_memory(nr_accounted);
> -	up_write(&mm->mmap_sem);
> +	if (tsk_is_oom_victim(current))
> +		up_write(&mm->mmap_sem);

How is this possibly safe? mark_oom_victim can run while exit_mmap is
running. Even if you cache the first read in the local stack, failure
to notice you marked it, could lead to use after free. Or at least
there's no comment on which lock should prevent the use after free
with the above.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-24 09:30 +0200
  Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-24 16:10 +0200
    Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-24 16:20 +0200
      Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-24 17:00 +0200
        Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-24 18:20 +0200
          Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-25 16:20 +0200
            Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-25 16:30 +0200
              Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-25 17:10 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-25 17:20 +0200
          Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-25 16:30 +0200
            Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-25 17:20 +0200
              Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-25 17:30 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-07-25 17:40 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-25 18:10 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-25 23:30 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-26 07:50 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-26 18:30 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-26 18:50 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-27 09:00 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-27 17:00 +0200
                Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-28 08:30 +0200
  Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-24 17:30 +0200
  Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-24 20:20 +0200
  Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-25 17:30 +0200
    Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-25 17:50 +0200
      Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-25 20:30 +0200
        Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-26 07:50 +0200
          Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Andrea Arcangeli <aarcange@redhat.com> - 2017-07-26 18:40 +0200
            Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko <mhocko@kernel.org> - 2017-07-27 08:40 +0200

csiph-web