On Mon, Jul 31, 2017 at 02:22:04PM +0200, Michal Hocko wrote:
> On Thu 27-07-17 09:26:59, Mike Rapoport wrote:
> > In the non-cooperative userfaultfd case, the process exit may race with
> > outstanding mcopy_atomic called by the uffd monitor. Returning -ENOSPC
> > instead of -EINVAL when mm is already gone will allow uffd monitor to
> > distinguish this case from other error conditions.
>
> Normally we tend to return ESRCH in such case. ENOSPC sounds rather
> confusing...
Well, I don't remember why I used ENOSPC in userfault_copy at the first
place, but if we are to keep it userfaultfd_zeropage should return the same
error...
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 96333187ab162 ("userfaultfd_copy: return -ENOSPC in case mm has gone")
> >
> > Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
> > ---
> >
> > Unfortunately, I've overlooked userfaultfd_zeropage when I updated
> > userfaultd_copy :(
> >
> > fs/userfaultfd.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> > index cadcd12a3d35..2d8c2d848668 100644
> > --- a/fs/userfaultfd.c
> > +++ b/fs/userfaultfd.c
> > @@ -1643,6 +1643,8 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
> > ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
> > uffdio_zeropage.range.len);
> > mmput(ctx->mm);
> > + } else {
> > + return -ENOSPC;
> > }
> > if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
> > return -EFAULT;
> > --
> > 2.7.4
> >
> > --
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>
> --
> Michal Hocko
> SUSE Labs
>
--
Sincerely yours,
Mike.