On Mon, 2013-08-05 at 16:38 -0700, Roland Dreier wrote:
> On Mon, Aug 5, 2013 at 4:31 PM, James Bottomley
> <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > I agree with the analysis. The fix is a bit draconian, though. A
> > workqueue actually runs in a kernel thread and there's a simple test for
> > that (!current->mm), so how about this instead (which is much less
> > intrusive)
>
> > ---
>
> > diff --git a/fs/bio.c b/fs/bio.c
> > index 94bbc04..e2ab39c 100644
> > --- a/fs/bio.c
> > +++ b/fs/bio.c
> > @@ -1045,12 +1045,22 @@ static int __bio_copy_iov(struct bio *bio, struct bio_vec *iovecs,
> > int bio_uncopy_user(struct bio *bio)
> > {
> > struct bio_map_data *bmd = bio->bi_private;
> > - int ret = 0;
> > + struct bio_vec *bvec;
> > + int ret = 0, i;
> >
> > - if (!bio_flagged(bio, BIO_NULL_MAPPED))
> > - ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
> > - bmd->nr_sgvecs, bio_data_dir(bio) == READ,
> > - 0, bmd->is_our_pages);
> > + if (!bio_flagged(bio, BIO_NULL_MAPPED)) {
> > + /*
> > + * if we're in a workqueue, the request is orphaned, so
> > + * don't copy into the kernel address space, just free
> > + */
> > + if (current->mm)
> > + ret = __bio_copy_iov(bio, bmd->iovecs, bmd->sgvecs,
> > + bmd->nr_sgvecs, bio_data_dir(bio) == READ,
> > + 0, bmd->is_our_pages);
> > + else if (bmd->is_our_pages)
> > + bio_for_each_segment_all(bvec, bio, i)
> > + __free_page(bvec->bv_page);
> > + }
> > bio_free_map_data(bmd);
> > bio_put(bio);
> > return ret;
>
> Yes, looks reasonable -- I can't think of any reason why anyone would
> ever want the bio code to copy to a random userspace address space.
>
> Acked-by: Roland Dreier <roland@xxxxxxxxxxxxxxx>
You did all the work ... just replace this patch with your previous one
and keep the original tags. (test it first, of course ...)
James
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