Re: [RFC][PATCH v3 6/6] fix wrong get_user_pages usage in iovlock.c

KOSAKI Motohiro
2009-04-14T06:58:00Z

> On Tuesday 14 April 2009 16:23:13 KOSAKI Motohiro wrote:
> > I don't have NET-DMA usable device. I hope to get expert review.
> >
> > =========================
> > Subject: [Untested][RFC][PATCH] fix wrong get_user_pages usage in iovlock.c
> >
> > down_read(mmap_sem)
> > get_user_pages()
> > up_read(mmap_sem)
> >
> > is fork unsafe.
> > fix it.
> >
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
> > Cc: David S. Miller <davem@davemloft.net>
> > Cc: Chris Leech <christopher.leech@intel.com>
> > Cc: netdev@vger.kernel.org
> > ---
> > drivers/dma/iovlock.c | 18 ++++++------------
> > 1 file changed, 6 insertions(+), 12 deletions(-)
> >
> > Index: b/drivers/dma/iovlock.c
> > ===================================================================
> > --- a/drivers/dma/iovlock.c 2009-02-21 16:53:23.000000000 +0900
> > +++ b/drivers/dma/iovlock.c 2009-04-13 04:46:02.000000000 +0900
> > @@ -94,18 +94,10 @@ struct dma_pinned_list *dma_pin_iovec_pa
> > pages += page_list->nr_pages;
> >
> > /* pin pages down */
> > - down_read(&current->mm->mmap_sem);
> > - ret = get_user_pages(
> > - current,
> > - current->mm,
> > - (unsigned long) iov[i].iov_base,
> > - page_list->nr_pages,
> > - 1, /* write */
> > - 0, /* force */
> > - page_list->pages,
> > - NULL);
> > - up_read(&current->mm->mmap_sem);
> > -
> > + down_read(&current->mm->mm_pinned_sem);
> > + ret = get_user_pages_fast((unsigned long) iov[i].iov_base,
> > + page_list->nr_pages, 1,
> > + page_list->pages);
>
> I would perhaps not fold gup_fast conversions into the same patch as
> the fix.

OK. I'll fix.