Re: [Qemu-devel] [Qemu-trivial] [PATCH v6 03/10] virtio-blk: fix reference a pointer which might be freed

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 18, 2014 at 03:49:22PM +0400, Michael Tokarev wrote:
> 14.08.2014 11:29, zhanghailiang wrote:
> > In function virtio_blk_handle_request, it may freed memory pointed by req,
> > So do not access member of req after calling this function.
> > 
> > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> > ---
> >  hw/block/virtio-blk.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> > index c241c50..54a853a 100644
> > --- a/hw/block/virtio-blk.c
> > +++ b/hw/block/virtio-blk.c
> > @@ -458,7 +458,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> >  static void virtio_blk_dma_restart_bh(void *opaque)
> >  {
> >      VirtIOBlock *s = opaque;
> > -    VirtIOBlockReq *req = s->rq;
> > +    VirtIOBlockReq *req = s->rq, *next = NULL;
> >      MultiReqBuffer mrb = {
> >          .num_writes = 0,
> >      };
> > @@ -469,8 +469,9 @@ static void virtio_blk_dma_restart_bh(void *opaque)
> >      s->rq = NULL;
> >  
> >      while (req) {
> > +        next = req->next;
> >          virtio_blk_handle_request(req, &mrb);
> > -        req = req->next;
> > +        req = next;
> >      }
> >  
> >      virtio_submit_multiwrite(s->bs, &mrb);
> 
> So, finally, I've applied this patch:
> 
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -469,8 +469,9 @@ static void virtio_blk_dma_restart_bh(void *opaque)
>      s->rq = NULL;
> 
>      while (req) {
> +        VirtIOBlockReq *next = req->next;
>          virtio_blk_handle_request(req, &mrb);
> -        req = req->next;
> +        req = next;
>      }
> 
>      virtio_submit_multiwrite(s->bs, &mrb);
> 
> and dropped Stefan's Reviewed-by on the way ;)
> 
> This is a bugfix after all ;)
> 
> Thanks,
> 
> /mjt


By the way, could you please add Cc qemu-stable on bugfixes
you have queued?
These are likely appopriate for 2.1.1.

-- 
MST