Re: [PATCH v6.15 3/3] ublk: enhance check for register/unregister io buffer command

[Ming Lei <ming.lei@redhat.com>]

On Mon, Apr 28, 2025 at 09:28:07AM -0700, Caleb Sander Mateos wrote:
> On Sun, Apr 27, 2025 at 6:50 AM Ming Lei <ming.lei@redhat.com> wrote:
> >
> > The simple check of UBLK_IO_FLAG_OWNED_BY_SRV can avoid incorrect
> > register/unregister io buffer easily, so check it before calling
> > starting to register/un-register io buffer.
> >
> > Also only allow io buffer register/unregister uring_cmd in case of
> > UBLK_F_SUPPORT_ZERO_COPY.
> >
> > Also mark argument 'ublk_queue *' of ublk_register_io_buf as const.
> >
> > Fixes: 1f6540e2aabb ("ublk: zc register/unregister bvec")
> > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > ---
> >  drivers/block/ublk_drv.c | 24 ++++++++++++++++++++----
> >  1 file changed, 20 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> > index 0a3a3c64316d..c624d8f653ae 100644
> > --- a/drivers/block/ublk_drv.c
> > +++ b/drivers/block/ublk_drv.c
> > @@ -201,7 +201,7 @@ struct ublk_params_header {
> >  static void ublk_stop_dev_unlocked(struct ublk_device *ub);
> >  static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq);
> >  static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
> > -               struct ublk_queue *ubq, int tag, size_t offset);
> > +               const struct ublk_queue *ubq, int tag, size_t offset);
> >  static inline unsigned int ublk_req_build_flags(struct request *req);
> >  static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq,
> >                                                    int tag);
> > @@ -1949,13 +1949,20 @@ static void ublk_io_release(void *priv)
> >  }
> >
> >  static int ublk_register_io_buf(struct io_uring_cmd *cmd,
> > -                               struct ublk_queue *ubq, unsigned int tag,
> > +                               const struct ublk_queue *ubq, unsigned int tag,
> >                                 unsigned int index, unsigned int issue_flags)
> >  {
> >         struct ublk_device *ub = cmd->file->private_data;
> > +       const struct ublk_io *io = &ubq->ios[tag];
> >         struct request *req;
> >         int ret;
> >
> > +       if (!ublk_support_zero_copy(ubq))
> > +               return -EINVAL;
> > +
> > +       if (!(io->flags & UBLK_IO_FLAG_OWNED_BY_SRV))
> > +               return -EINVAL;
> 
> I would still prefer to see this common UBLK_IO_FLAG_OWNED_BY_SRV
> check moved to __ublk_ch_uring_cmd() along with the existing flag
> checks. Something like this:

This way mixes bug fix with cleanup.

We are close to v6.15-rc5, and bug fix should keep simple for minimizing
regression.

But it is fine to make it one cleanup aiming at v6.16.


thanks,
Ming