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Date:   Sat, 23 Dec 2017 08:31:35 +0100
From:   Dmitry Vyukov <>
To:     Andrea Arcangeli <>
Cc:     Andrew Morton <>,
        Eric Biggers <>,
        Mike Rapoport <>,
        LKML <>,, Al Viro <>,
        Linux-MM <>,
Subject: Re: [PATCH 0/1] Re: kernel BUG at fs/userfaultfd.c:LINE!

On Sat, Dec 23, 2017 at 1:25 AM, Andrea Arcangeli <> wrote:
> Hello,
> Thanks for the CC, I'm temporarily very busy so if there's something
> urgent, safer to CC.


syzbot uses and for fs/userfaultfd.c you are not
there, so if you want to be CCed please add yourself to MAINTAINERS.

> This passed both testcases, the hard part was already done. I'm glad
> there was nothing wrong in the previous fix that had to be redone.
> Simply we forgot to undo the vma->vm_userfaultfd_ctx = NULL after
> aborting the new child uffd ctx, the original code of course didn't do
> that either.
> Having just seen this issue, this isn't very well tested.
> Thank you,
> Andrea
> Andrea Arcangeli (1):
>   userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK
>     fails
>  fs/userfaultfd.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)

The original report footer was stripped, so:

Please credit me with: Reported-by: syzbot <>

and we also need to tell syzbot about the fix with:

#syz fix:
userfaultfd: clear the vma->vm_userfaultfd_ctx if UFFD_EVENT_FORK fails

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